This was a question I had too when my AS left rehab. I received a great deal of advice from the rehab on this subject; they stressed that my AS's focus should be on recovery and little else for a minimum of 90 days.
That said I knew they discussed his plans and he put together a recovery plan with them before leaving. The plan was not what they suggested and there were several elements of it that I wasn't thrilled about because I thought he was taking on too much "real life" activity and not enough recovery work. But you know what......I let it be. He needed to draft his own plan for reengaging with the world and I just said "I trust you will do the right thing for yourself".
Within his plan he took my boundries into account....sober = school tuition and support; using = no support and no tuition.
He went back to school, moved into a place by himself, joined a gym and is going to meetings and seeing a therapist. It is a lot....and there are days he feels overwhelmed but he is making a success of it and doing it his way. His take is keeping busy and having school to focus on gives him a reason to be sober and work his recovery.
I think that this is a very personal choice but I see the value for my son in accomplishing things on his own - it supports his faith that he can maintain his sobriety.
Everyone is different but I figure if my boundries aren't being breached then whatever he chooses is just fine.