To return to the first post.
He has quit smoking weed & has got a job interview.
Was this all his choice?
If so it sounds like "he" is trying to pull himself together & get on with his life properly instead of flying it away.
So if he fails this interview, perhaps it's not the best time to kick him out & let himd rop back down to weed smoking lyabout, because that's what will happen as he gets a state provided flat etc.
Encourage him further to go for mor job interviews & stay on the staright & narrow, if he screws up after that..... then kick him out.