This term replaced "subprime" and looks a lot different than subprime loans of the past.

I think your goal of getting your first RE investment for around $50k is doable as long as you plan to leverage debt (Loan). 

Most non-FHA loans will require at least 15% down but you'll have to have amazing credit.

Or, depending on the property you could go non-QM with like a DSCR loan and close in an LLC or partnership.

If they can afford to stay, chances are they need to refinance and get the X name off the loan.   

I doubt he'll be able to quality for a loan (VA) with just his income. 

10% down 2nd home loan and savings from the proceeds of already owned STR's.

If I got a home equity loan for Property 1 and used the proceeds as downpayment for Property 2 and then got a 2nd loan for the remaining 75% purchase price for Property 2, when I sell Property 2, can I use the Property 1 loan as part of the cost basis for computing Property 2 capital gains?

They will go up to 100% loan to value or LTV (or used to). 

Minimum loan amount is $250k.