RN I read your posts and my heart just aches for you...I see my own boy - same age - and think of how I'd feel if he had asked to come home. I know how very, very hard it must be. But I think you have a great plan in place. Successfully complete the rehab, he'll have some $$$ in place for living expenses (BANK THAT MONEY)! Let him come home, find work, and then find his own place. He'll know it's short-term. He'll know that he can't live with you forever. He'll be in a new place too...away from old, bad influences.
I hope your visit goes well. Hang in there. 