If this is not the case, then assuming there is sufficient equity, the trustee might obtain a secured cash out loan against the property (probably at higher rates then conventional commercial) and after the loan funds, the trustee would then distribute the cash to the siblings who want to be bought out, and the 4plex to the sibling who wants it with the loan still in place. 

I paid cash for my first building and am seeking a loan on this second property so I can scale a bit faster.

The sales proceeds close out the monetization loan and the deal is complete.Monetized Installment Sales were covered on BP here... https://www.biggerpockets.com/forums/51/topics/569...

If I have a 6 months gap can I still be qualified for a loan to rent properties?

On our personal Single Family investment homes we are able to barely cashflow with the higher rates with new acquisitions (we use commercial loans so our rates are prime +1%), but happy with with capturing some good equity on the purchase.

You could assume their loan but this depends on what they still owe.

In addition, that increased down would take many years (likely longer than the 30 year loan term when including modest 5% growth on the money) to pay for in the increased cash flow. 

Next step would be finding a lender and figure out which loan type.

The property is currently under an FHA loan locked in at 2.5%, which means I am unable to sell or refinance at this time.

If you master creative financing you can find 0% down deals.In 2023, I purchased 73 units with seller financing and 44 of those were 0% down loans.4.