The unit is within blocks of Harvard University and a billion other universities are within a few miles.

@Jed Butikofer You need to find a market that has decent cash flow (think $200/unit/month) and become an EXPERT on that location.

So, landlords of exempt units don't even have to be concerned at all.   

I haven't booked anyone from FF this past year, but I might keep one unit open to keep the conversation open.

I'm not in that market so I can't speak specifically to it, but to me the deciding factor would be what the surrounding units and area has. 

.- Tell them they have to provide documentation of the animals service / emotional support (as allowed by your local ordinances), and that they have to provide documentation that the animal is current with its inoculations, etc. as well as its local license before you'll permit the animal in the unit.- Tell them they'll have to provide you with a copy of their renter's insurance naming you as additional named insured, with a minimum of (I use $300,000) liability insurance, also before they move into the unit.It's not perfect, but it's a start toward a tenant transparency.

If you are talking 100+ unit apartment complexes, then I would change my tune a bit.What is more important than the actual market, is the dynamics within that market?  

Live in one and rent the other units out!

I'm born and raised in Houston and now work with a full service long-term rental management managing over 300 doors - all SF or MU (up to 4 unit).

Else, move to a smaller unit or take in an extra roommate.