I got help because of my child. Getting help was scary. We all did it together (my husband and I) the first try's were spectacular disaster's. If it came from my parent I would have been against it. I had my child at 18 he was planned like your son is trying. We had a stable house to live in and we quickly lost that as my health declined. We struggled and moved for years but we never let our family know. Now we're actually stable housing wise and have been for awhile.
All this to say don't keep bailing your son out. Give him a list of resources and numbers and tell him you can no longer help him with bills Unless he's full time school (votech or college).