If he wants to move in with you and you're all right with that, he can use all of the support he can. You may encourage him to get help for his depression and drinking and doing positive things. He can sleep on the couch.
As long as you think that the move will be positive and you will not be enabling him in any way, then discuss with him some of the responsibilities he would have in your home.
Dr. Rossi..... I am satisfied with your answer! I just needed some reinforcement on making this decision. It saddens me to see him suffer. He does need help. Setting boundries is good advice, meaning....encouraging help and all. Thanks!