Most inlaws do not have a full kitchen- but they can have a kitchenette. They also need to have a common/ interior door- that can have a lock on it- that connects the main house to the in-law wing. Also, most inlaws are on the same heating system and electric meter as the main house- which differentiates it from a 2-family setup.
If you can rent it to someone under these terms- not a full kitchen, a common door with you and your family, and you want to pay for their heat and electricity, etc- then maybe you should consider it. But see what the rules say first.
If I can be of any other help, please let me know. Thanks and good luck,