I agree... Let's be honest here. If you go after him for a lease termination fee, you'll piss him off most likely. Your monthly rent stops. You have to take him to court and spend way too much energy on something that is easily avoidable as long as he keeps paying monthly rent. Maybe he still wants the place but moved stuff to another place for the summer and wants to come back in August or something. As long as the money's coming in, don't ruffle the feathers.