Some might suggest, as I'm sure he would, that he is almost an adult. That don't cut it either. YOU are the source of his life and all things flow from you. If he is still living at home, mom doing his laundry and cooking his food and so on , then he hasn't learned how to dry behind his own ears. He doesn't know as much as thinks he does, nor does he recognize that you DO. This is the same whether he were 25 or 17. If he can muster no better action than to be "hanging out" and living at home, then he isn't fully ready to join the rest of the world.
On the other side, he does not want to stay close to home because he is primed by culture and biology to GO. It is the Human Charter to GO, so that they can DO something and BECOME someone. Instinctively, he knows he must go... even if he isn't quite ready. In essence he is conflicted - that's reality. It is in all of us.
What choices he makes now are the most important he will ever make. Nothing you can build, including a home or a life, is any better than it's foundation.
So keep praying and having courage. Keep driving your point home. At this point he isn't adept enough to make all the right choices on his own.