Take the money off the table, here.
None of us can control other people and their choices. We can control ourselves.
It's your choice who you permit to live with you, or not.
We all know addiction is progressive. It's your choice whether or not you want to live with someone in active addiction and all the craziness that goes along with it, or not.
Your son is the master of his own life. It's his choices, not where he sleeps, that determines his outcome.