RPHYX of course now closed.
Here's the August 24, 2021 supplement to the fund prospectus:

August 27, 2021 (the "Revised Closing Date") ...
After the Revised Closing Date, the following eligible investors may also open new accounts:
· New shareholders may open Fund accounts and purchase shares directly from the Fund (i.e. not through a financial intermediary).
· Any trustee of RiverPark Funds Trust, or employee of RiverPark Advisors, LLC or Cohanzick Management, LLC, or an investor who is an immediate family member of any of these individuals.

https://www.sec.gov/Archives/edgar/data/1494928/000139834421016711/fp0068207_497.htm

After LOTS of screening and test driving in these areas:
Own ST/ST HY: LALDX (thanks to another poster, and that also lead me to research and own MS LBNDX) and RPHYX, both provide consistently boring, consistently positive TRs for monies awaiting a better home. IMO, these are two of, if not the very best for the job I assigned them: inch forward and don't lose me any money. RPHYX of course now closed.
Likely the next to be added to that group with similar pedigree: PFIIX/PFIAX.
Also own HY: BGHIX (owned it a while as DHHIX), VWEHX and FAGIX.
Others in ST/ST HY cat's that may come aboard: IOFIX, BUHFX, TUHYX, RCTIX.

. Also RiverPark has RSIVX…somewhat longer duration than RPHYX, but performing relatively well this year it seems.
Honestly, if you’re ok with courting risk, IOFIX is as steady as they come ....

RSIVX is doing great this year; hadn't thought about it in a long, long time. It's been a dog for most of its life, but must be doing something right this year. Will look into it.
Agree on IOFIX too. Several other securitized OEFs have fallen off the pace lately, but it's keeping on keeping on.
JD's RCTRX suggestion looks pretty good in securitized, too - never heard of it till this thread.

OSTIX, Osterweis Strategic Income (TF at most brokerage houses)…..or ZEOIX, Zeo Short Duration Income (also TF). Also RiverPark has RSIVX…somewhat longer duration than RPHYX, but performing relatively well this year it seems.
Honestly, if you’re ok with courting risk, IOFIX is as steady as they come (the once-in-a-decade, plus, COVID crash notwithstanding….). 4-5% yield and it generally goes up or stays flat most days. I know it’s not high yield! Don’t kill me for suggesting it haha.

FWIW, in my withdrawal account, which I haven't had to use yet, I hold RPHYX as the cornerstone, about 35% of the account, but other short/ultra-short deration ETFs I use are JPST, FLRN and MINT.

I use RPHYX and FPFIX for short-term bonds. Not expecting much at all - maybe 1.5% to 2% annual returns in the current interest rate environment. Better than nothing, but not by much.
I balance these steady funds with higher risk (but low duration) vehicles RCTRX and JSVIX.
Recently sold all of my MWFSX.

Out of curiosity, just checked which OEF holdings contribute significantly to my bond allocation (other than RPHYX which I use as a cash substitute -- NTF at Fido so easy to sell and buy). FWIW, in high to low order:
SVARX, RCTIX, CRAAX, PTIAX, PONAX, VWINX, BGHIX, FIRNX.
SVARX was added to my portfolio about a year ago. It appears well suited to the current market environment and would probably be the bond fund I would be most interested in adding to at this point (but would need to consider it is TF at Fido).

My "cash account" currently includes RPHYX, ICSH, and FZFXX. I was at 67% equities at the start of the year but am currently up to 70% despite some previous YTD stock trimming. Thus, the thought of trimming stocks back again now to add a little more to the cash account. The economy appears to be continuing to improve. But the Delta variant, the possibility (probability?) this was the peak quarter for corporate earnings, the ongoing chips shortage, probable upcoming measured tapering by the Fed, uncertainty concerning future interest rate increases, the ongoing crackdown on corporations in China, and the "temporary" price surge are at minimum "wall of worry" problems to consider with a "richly" valued stock market.

Another filing as of 8/24/21:
https://www.sec.gov/Archives/edgar/data/1494928/000139834421016711/fp0068207_497.htm
497 1 fp0068207_497.htm
RiverPark Funds Trust
RiverPark Short Term High Yield Fund
Institutional Class (RPHIX)
Retail Class (RPHYX)
Supplement dated August 24, 2021 to the Summary Prospectus, Prospectus and Statement of Additional Information (“SAI”) dated January 28, 2021.
This supplement provides new and additional information beyond that contained in the Summary Prospectus, Prospectus and SAI and should be read in conjunction with the Summary Prospectus, Prospectus and SAI.
IMPORTANT NOTICE ON PURCHASE OF FUND SHARES
Further to the Supplement dated May 20, 2021, effective as of 4 p.m. on August 27, 2021 (the "Revised Closing Date"), the definition of existing shareholders who may purchase Retail and Institutional Class Shares of the RiverPark Short Term High Yield Fund (the "Fund") is modified as follows:
Existing shareholders will only include shareholders of record of the Fund as of the Revised Closing Date (although if a shareholder closes all accounts in the Fund, additional investments into the Fund may not be accepted).
After the Revised Closing Date, the following eligible investors may also open new accounts:
·New shareholders may open Fund accounts and purchase shares directly from the Fund (i.e. not through a financial intermediary).
·Any trustee of RiverPark Funds Trust, or employee of RiverPark Advisors, LLC or Cohanzick Management, LLC, or an investor who is an immediate family member of any of these individuals.
The Fund reserves the right, in its sole discretion, to determine the criteria for qualification as an eligible investor and to reject or accept any purchase order. Sales of Retail Class Shares and Institutional Class Shares of the Fund may be further restricted or reopened in the future.
PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

Makes sense. Using the MMA as a buffer reduces the number of transactions with RPHIX. That not only cuts down on transaction fees, but reduces the headache of keeping track of cap gains. And over the period of a year or so, you should not lose money due to minor fluctuations in the share price of RPHIX.
You surely already know this, since you're currently using TRBUX and PRWBX.
Another advantage of RPHIX over RPHYX aside from lower ER is that, should you need the cash quickly, Schwab won't charge you a short term redemption fee. Brokerages typically add that transaction fee on some NTF fund trades.

Schwab’s short-term redemption fee will be charged on redemption of funds purchased through Schwab’s Mutual Fund OneSource service (and certain other funds with no transaction fees) and held for 90 days or less.

https://www.schwab.com/public/file/P-6374145
Also, some fund families are a bit flexible about how much money they require you to keep in the account after you open it. You might check with Schwab and/or Riverpark to ask how low you can let your balance go.

Keep in mind that the magnitude of the final difference over ten years is affected by the volatility of the returns and by the magnitude of the returns. Just a way of saying that past performance is not a guarantee of future results.
I prefer instead to look at the 0.25% difference in ERs and estimate my breakeven point. For a $50K investment, $50 represents 10 basis points (0.1%). So it would take about 10/25 of a year, or around five months, to break even. Anything after that is gravy.
At Fidelity, you could make incremental additions for $5. So you could add $5K at a time and still have a 5 month break even point.
If volatility and rate of return didn't matter, you could just compare a 0% return on retail shares with a constant 0.25% return on investor class shares after subtracting $50.
This simplistic calculation gives you:
RPHYX: $50K x 1.00 ^ 10 = $50K at the end of 10 years.
RPHIX: $49,950 x (1.0025) ^ 10 = $51,212.89 at the end of 10 years.

How much would a $50,000 investment in RPHYX, expense ratio of 1.05 lose over a 10 year period compared to RPHIX expense ratio of .90? RPHIX would have a transaction fee of approximately $50 at Schwab.

Bobpa,
FWIW, I put RPHIX and RPHYX, on the M* Interactive Performance Chart, and for the total existence period (9/30/2010 through 06/11/2021), the chart shows total return for an initial $10,000 investment as $13,632 for RPHIX and $13,237 for RPHYX. That is a difference of $395, multiplied by 5 to get the $50,000 investment, and it equals a total difference of $1975 more for RPHIX over the history of the funds. Trying to get down to the impact of a $50 transaction fee, in 2010, is beyond me, since I don't think M* tries to guess what the transaction fees, if any, are at the many different brokerages--which often negotiate transaction fees differently for different investors (I pay $25 transaction fee at Schwab, per a negotiated account opening, along with some extra cash that I got from Schwab to open an account over a designated amount)

How much would a $50,000 investment in RPHYX, expense ratio of 1.05 lose over a 10 year period compared to RPHIX expense ratio of .90? RPHIX would have a transaction fee of approximately $50 at Schwab.

Absolutely @hank. Cash alternatives, as long as you are ok with the risks that short term bonds can lose money too. That is likely the case if inflation takes hold as predicted. BSV is a popular short term bond fund from Vanguard and last I look it was slightly under water for the year.
Right now I hold MINT, BSV, JPST, FLRN and RPHYX in my withdrawal bucket. RPHYX has of course been a favorite on this board and with David Snowball for a long, long time. It's been closed most of it's existence but has been open for about a year now. It is closing again this month to new investors (if it hasn't already).

I find very little that I am comfortable with, at present, for a long term buy and hold investment. As a result, I have become more of a reluctant trader, focusing on bond oef categories that are doing well overall, that I think will last at least 3 months, and hopefully longer. I have been using several nontraditional bond oefs for trades--some more risky than others. Recently, I have chosen to open up positions in FR/BL bond oefs, as inflationary issues seem to be growing in frequency. FR/BL do well when interest rates stay flat, or increase, and over the past year FR/BL have been doing well. Nonagency mortgages were outstanding fund choices for much of the last decade, but they can be risky and many of them did not do well in the black swan crash in March 2020, but starting in April of 2020, they have been outstanding rebound investments, and now are settling back into a performance pattern, resembling the last decade--as a result I use funds like SEMMX as a short term aggressive trade choice, but don't trust it for too large of a position. I have short term trade positions in HY Munis, but in general I do not find HY Munis as a category I can trust for long term--when it comes to the fall, around September/October, HY Munis often get clobbered because of seasonal pressures. With HY Munis, I got clobbered early after the March 2020 crash, and so I limit how much I will put into this category, and ususally with a time limited criteria in mind. For my more conservative taxable account, I will use a fund like RPHIX because of its long term performance record, in good and bad markets, but do not use it as a trade vehicle because of fees--RPHIX/RPHYX is scheduled to close to new investors, but apparently stay open to current investors. Another fund I use in my taxable account is the very aggressive short term bond oef, DHEAX. I sold it during the March crash, but bought it back later in 2020, and have held it since. It is risky, and the DHEAX management will not permit frequent trading, so when I own it, I plan on holding it for at least 3 to 6 months--but I will sell it after that time period if market conditions merit that.

Think of traditional bank accounts. There's a checking account where you can write checks, pay bills, buy things. And there are savings accounts that pay higher interest.
You can keep all your cash in a savings account, but when you need to buy something, you transfer the cash to your checking account. (Technically some transfers from savings accounts are limited, but we'll ignore that detail.) The point is that there's a difference; you can't use a savings account in exactly the same way as a checking account.
Same thing here. You can use an ETF as a savings account. But you're going to have to manually move money into the "checking" account (core fund) if you want to use it. And with an ETF, it's going to take two days before you can take the money out of Fidelity. (You can use the ETF proceeds for trading almost immediately - different brokerages handle this slightly differently and I'm not positive about Fidelity's rule here.)
There's also the matter of tracking cap gains. @Investor had a subthread (under RPHYX) that covered this a few days ago. But you already know this, as you've been using a TRP short term fund this way. Likewise you also know that these funds fluctuate in value.
ETFs, especially when used for cash and traded short term have additional costs. Notably spread. The spread on FLDR is sizeable: 0.06% (on average). If you were to buy $100 and immediately turn around and sell it, you'd lose around 6¢. You might pay $100.03 to buy the fund and receive $99.97 when you sold it. You could try to mitigate that by placing limit orders, but then you run the risk of seeing some of your orders go unfilled.
6¢ might not sound like much, if you're doing this even once a month, that's nearly 3/4% eaten up in transaction costs.
If on the other hand you're letting most of the cash sit (so you're only losing 3/4% on a small part of the cash), then you don't need usually need instantaneous access for much of the cash. In that case, you could still use a short term bond fund for your cash reserve.

That works for me. I have enough $'s in FZFXX for a little quick trading. But the rest of my "cash" $'s are in ICSH, JPST, and RPHYX. FLDR is too volatile for my cash $'s.

M* Link
RPHYX has done the best of my 4 cash holdings this year (but it can not be traded during the day and has a minimum holding period):
RPHYX Link

I am thinking of utilizing RPHYX for some cash in a taxable brokerage account. I used this fund in retirement account so I did not care much about tax efficiency and cost base accounting. But in a taxable account one needs to be more careful not to be surprised.
Any tips on using RPHYX in a taxable account?

RPHYX Like others on this site, I use the fund as a cash substitute.

https://www.sec.gov/Archives/edgar/data/1494928/000139834421011115/fp0065693_497.htm
RiverPark Funds Trust
RiverPark Short Term High Yield Fund
Institutional Class (RPHIX)
Retail Class (RPHYX)
Supplement dated May 20, 2021 to the Summary Prospectus, Prospectus and Statement of Additional Information (“SAI”) dated January 28, 2021.
This supplement provides new and additional information beyond that contained in the Summary Prospectus, Prospectus and SAI and should be read in conjunction with the Summary Prospectus, Prospectus and SAI.
IMPORTANT NOTICE ON PURCHASE OF FUND SHARES
Effective as of 4 p.m. on June 18, 2021 (the "Closing Date"), Retail and Institutional Class Shares of the RiverPark Short Term High Yield Fund (the "Fund") are closed to new investors.
After the Closing Date, existing shareholders of Retail and Institutional Class Shares of the Fund and certain eligible investors, as set forth below, may purchase additional Retail and Institutional Class Shares of the Fund through existing or new accounts and may reinvest dividends and capital gains distributions.
Existing shareholders include:
• Shareholders of record of the Fund as of the Closing Date (although if a shareholder closes all accounts in the Fund, additional investments into the Fund may not be accepted).
• Clients of a financial adviser or planner who had client assets invested in the Fund as of the Closing Date.
After the Closing Date, the following eligible investors may open new accounts:
• New shareholders may open Fund accounts and purchase shares directly from the Fund (i.e. not through a financial intermediary).
• Any trustee of RiverPark Funds Trust, or employee of RiverPark Advisors, LLC or Cohanzick Management, LLC, or an investor who is an immediate family member of any of these individuals.
The Fund reserves the right, in its sole discretion, to determine the criteria for qualification as an eligible investor and to reject any purchase order. Sales of Retail Class Shares and Institutional Class Shares of the Fund may be further restricted or reopened in the future.
PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE.