For comparison, a Navy Federal FCU personal loan will be in the 15s%

@Luke Hamlin you can buy a second home with 10% down with a Conventional loan.

Let's say you borrow $100,000 to pay off your $50,000 IRA loan, $25,000 on credit cards, and keep $25,000 for finishing renovations.

the rest of the loan payment right now is coming back to you eventually. 

The SST doesn't apply for legal 2-flats so if you want to use FHA it's probably better to target those that maybe also have a non-conforming basement or attic unit.This is why the 5% down conventional loan is a game changer for house hackers.

So for the first property which will cost over $1 mil to construct, there will be stacked loans, essentially $280K will come from loan assistance program,( the name is not correct but the same idea).

They were thinking of planning another one that required massive loans (7 figures). 

Explore FHA loans and mentorship opportunities from experienced investors.

I recommend that you find a trusted or recommended Mortgage Loan Originator (MLO), who can give you options for property-based loans (mostly investment loans) and they don't use your taxes but the P&L of the property.

If you did finance some of the purchase using a non-recourse loan, then you need to read up on UBTI/UDFI and there are some taxation benefits that the IRA can achieve since it now owes taxes in that scenario.