Reverse inlaw apartment?

[William Shomphe]

Whatsup BP, first post, long time listener and lurker. I'm out here in metrowest Massachusetts trying to get my feet wet in REI. I have a question that I obviously should ask my lawyer and town, but wanted to hear some of your opinions about this. I'm in the middle of constructing a large garage at my first brrrr house that I already have completed. It will be a 2 story with an open concept living quarter upstairs. Mancave-esque you could say. I am not in a zone approved area for such a rentable apartment but am having family move in for a few years. My question is this: If I had a SFR with said garage, and I personally lived in the in law apartment but rented the house out, instead of the opposite, would that be considered a loophole or still just flat out illegal? Again, I know who to ask so play nice, I'm just seeing if anyone has attempted this. Home and arrangement are not long term, just looking to recoup some money faster than currently generating while still paying the bills.