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).

Plus the mortgage company probably calls the loan, and if you can't pay it off then you can lose the property.

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.

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

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.

Explore FHA loans and mentorship opportunities from experienced investors.

The deal will leave the seller at your sons mercy for decades (the life of the loan).

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

(Even went beyond the second page of Google.)I have an investor who wants to partner on a deal by providing a loan for the down payment.

To maximize your investment, use financing options like FHA or conventional loans, analyze deals based on cash flow and cap rates, and network with local investors through REI meetups and BiggerPockets.Good luck!