Why did he sign the lease if the floor and the paint on the walls was ugly? He did view the place before he signed the lease? Let him move out, but you don't have to give him all of his money back. Prorate the rent and hold the security deposit until he moves out and cleans the place to as well as it was cleaned when he moved in. Make sure he has not ripped anything up, or caused any damages. I would probably just give him half a month rent back, since it sounds like he will have the place for half of the month.