Even the credit union must do this, their regulator does not allow them to give 3% down loans with MI coverage. 

I highly recommend you do your research on the regulations.  

Just food for thought as I always see people mention 1031 exchanges on here and in podcast but rarely have ever heard anyone mention anything about the Reverse 1031 exchange.To me that seems much less stressful honestly as the REIT I work for did at least 2 in 2018 with our shopping centers and plan on doing many more.Instead of selling your property and having to rush into throwing into another with a reverse 1031 exchange you first purchase the property you desire and then you can sell your property to cover it.Obviously there is more rules and regulations than this but that is the simplest way to explain it and gives you something to look into.  

The therapist told us it would be good to keep him in a stable environment (he has never been in one...

Sam,It all comes down to local regulations, zoning...I would be at the City/County planning office first thing and see what's allowed, what the process is...where I live (Bend, Oregon) ADU's are very regulated, but other areas just outside of town are totally different...Good luck...Adam

It’s a personal choice if not regulated by your state or city.  

You as a contractor supply the contract which covers you and follows local laws and regulations .

I can't speak to your specific questions, since I'm not familiar with the rental regulations in the UMD area.

I know that this is outside of the regulations of what the city of Austin considers a short term rental which is less than 30 days.Im concerned that it might be foolish to rent 30+ days without a traditional deposit and lease.

There are a lot better ways to fund college in a tax favored environment than 529s.I can share more if need be.