This sounds like a recipe for a family fight later unless you are an only child.

Yup....trading off $70k/year/child is a pretty big deal.  

Tenant screening costs anywhere from $35 to $55 per person should include a credit report, criminal background check, eviction check,  and in some cases prospects are run through a terrorist and a child abuser data bases.

that 100k will be our down payment for our next home which will place our next home's budget within the 350-400k sale price...the X factor is my wife is pregnant with our second child. 

Real estate has been in my family since I was a child.

On the other hand, if the son just turned 18 and has been living in the apartment with mom since he was a child, I would not require an application (and you probably don’t have legal grounds to force him to complete one in this scenario). 

That seems fine to me because I know there is a market for that--young singles, young couples and even possibly single mothers with one child.

But what about IRS, child support, or federal court judgements?

If the borrower is low-income and/or a senior and gets legal help, it could be child's play to rip apart the lender's foreclosure and loan.A lot depends on the agreement and paperwork the seller/lender has with the borrower.  

She's the only child and she said she thought her name was on the loan.