Here are two items from mine that deal with your issues:14.

Since you're rehabbing a property, I would not expect your capex and maintenance items be that high, but if that makes you feel more confident, keep running your numbers as you see fit.

Usually once a thread gets past the first page, either the persons original question has already been answeredThere have been several follow up questions askedAn entirely new discussion (debate) has broken out in the ensuing pagesAs a result of these things if I don't read all of those long threads I view my post as being non-value added to the conversation, so I don't make it. 

We'll have had what seems like a valuable conversation, and then they will ask what color house I prefer, or what the "1% rule" is, or if I prefer wood/metal fences.

One is in Converse, TX which is also a suburb of San Antonio. 

What's the bet that you're paying a much higher interest rate on that car loan (for what is essentially a consumable item) than if you'd bought it with proceeds from a HELOC on a property that you (could have) wisely bought first?

(2) What items to check during due diligence ?

You'll be ahead of the game by skipping an architect and going straight to a self storage conversion kit manufacturer like Trachte or Janus. 

I’d do right by my family first, which means a detailed conversation with my mother that focuses on her situation and her wants and needs.

:)(I don't know that specific market or what a studio garage conversion goes for... maybe only $625/mo and it's "only" 25% CoC ROI that he's looking at...)