If it were me, I'd rather give him a couple months more at my house than spend thousands of dollars setting him up in a new place. It was supposed to be situation where the homeowners would be getting a little extra money from the brother-in-law, not spending money on him, regardless of whether they can afford it. 

He needs to get a roommate and find a place he can afford without the homeowners bending over backwards and/or spending their savings to make it happen.