From your OP, I would suggest that the issues are more to do with the mother, not the son.
Is he the youngest son? - if yes then the above rings true - Mummy not letting her baby grow up?
Unfortunately if he has not worked by the age of 29 it is unlikely that he will ever do so. Even if he did move out then he would probably be back on the scrounge very time a bill was due.
it shouldn't be too much bother to find him a wee cooncil flat and get housing benefit too
I think that as he is under 35 he would only be entitled to a room in a shared house rather than a flat - this is how it works near me.
Unless the mother is willing to start showing some "tough love" - i.e. boot him out and make him take responsibility for himself I would steer clear.