I've been here a couple times before. Tell him that he's had a plenty of time to make things happen for himself, you can't do anything else for him, your part is done... he's gotta go. Depending upon what you've already talked to him about, you can set a deadline or not. Either way, I'd at least show him where he CAN go... a local shelter or gospel mission, etc. Just tell him you're done. It was never about what you were supposed to do for him in the first place. It was only ever supposed to be about him being able to get up and out on his own two feet. Three months is long enough. Believe me, if you give him any more time, he'll just keep taking it. Set him a deadline (no more than a week or so) and stick with it. Find him someplace else he can go if/since he can't figure it out for himself. Then wipe your hands clean of it. There's only so much you can do. The blame lies solely on him for not making good use of your good graces and taking his own steps and walking out on his own. You've more than done your part. Once he does make things happen for himself, he will thank you. Plus, I'd bet that your mom doesn't need the added stress, and she certainly didn't come to this point in her life to have to deal with this. Be there for her, above most.

Be holy.