Thanks again all for your replies. It does really help. His doctor is pressuring me to find him housing or he won't get the Assisted Outpatient Treatment. He wants an answer by tomorrow. I am sitting with it and praying for clarity. The insight shared from others really does help.
I know fully what I am getting into. It ultimately won't work. But the choice is am a willing to do it without resentment. (That may be a no - thanks Recovering). My mother and father were drug addicts - I took care of them. My son's father is an alcoholic - I left him. Now my son the most difficult of all. It's just horrific to have to make this choice. It's comforting to know that I am not alone.