Just throwing out ideas at this point. 

Get a lawyer to draft a 2nd position lien secured by this property. 

Lenders who have posted here care to comment.See belowLimits on the Number of Financed PropertiesIf the mortgage loan being delivered to Fannie Mae is secured by the borrower’s principal residence, there are no limitations on the number of other properties that the borrower will have financed.

And you'll need a deed of trust to secure the note to the property. 

And balked when I included normal verbage in the PA that the security deposit $XXX and pro-rated rent would be turned over to me at closing. 

If he just keeps throwing tar and caulking at it and hoping to find the leak, I would go call in another roofer ASAP to get an estimate on fixing it.

IF there is a recession not having the house of cards that is debt will put you in the most secure position, however just having the ability to purchase will probably be enough because in a recession sellers would have a harder time selling properties and in a true recession you wouldn't have an absolute ton of competition from cash buyers like the case is now.

I am not an expert on all of the securities law issues, but I have seen gifting of interests in syndication deals to a limited partner's children (cannot confirm that they were minors). 

If I become a Co-Borrower on a loan secured by a property that I intend to exchange into, will that prevent me using the 1031 Exchange?

The DOT secures the mortgage/note and outlines the foreclosure process in Texas.