How much discretion do we have in renting owner-occupied duplex?

[Eryn MacDonald]

We live in the top unit of a 2-family and rent the lower apartment. We were required to take a landlord class when buying because of the mortgage program we used. We got it rented pretty much immediately and those tenants stayed for ~7 years, with almost zero problems, which was great for us! They just moved out and we’re looking for new tenants. However, because it’s been so long, I’ve forgotten some of the details about what additional discretion we have as owner-occupants. 

I’ve been doing reading, but other than not being required to rent to people with children, I am not seeing much. We live in a pretty high-demand area and our place is probably a little nicer than others in the price range, so we’ve had a lot of interest. My issue is that we  showed the apartment to a bunch of people over the weekend (I wanted to get it over with and didn’t want to risk not getting anyone good) all of whom filled out applications, and I’m confident that several of them will easily qualify. So if that’s true, how do we choose? Are we allowed to take into consideration who we think will be most compatible to live upstairs from? Do we just have to take the first qualifying application we received? None of this is related to protected classes, just the “vibe” I got from meeting people as far as how easy/demanding they’d be to deal with. We’re in MA, and I know it’s stricter here than a lot of places. 

Thanks for any advice.