Let's clarify this a bit.
-Jay mentions he's moving to Ann Arbor and could use a place to stay for a couple days, week maybe.
-I'm living in a house for 8 people with only one other roommate as it's the last month of summer and everyone else is back home, so I figure why not.
-Jay moves in, and stays for a few weeks, up to the point where my roommates start moving back in.
-From there, we don't really have room, but I'm leaving for my brother's wedding back home, so I tell him he can take my room for one more week if my roommates are cool with it.
-I get back from my trip and Jay's still there.
-School starts, Jay's still there.
-We tell Jay if he wants to stay with us he has to start paying a bit of rent (something like 200 bucks a month to sleep on our couch).
-Jay moves out within 3 days.