You've said, "He", so no need for clumsy 'theys' and 'thems'.
I do know two families with adult daughters, both of whom lost their confidence, one at seventeen, still at school, the other during the second year of university. Parents were loving and nurturing, various types of help tried to no avail. The girls stayed at home, the eldest now pushing fifty living with widowed mum and the youngest in her forties, with mum and dad.
Both girl took over housekeeping, some cooking, decorating and gardening at home which was extremely helpful while parents were working. What's more they did, and do, it very well. The eldest of them had a very sick father and she and her mother cared for him at home for quite a while before he died which was much appreciated. She and mum have now moved to a different house and daughter runs the show.
If you met either of them you would not think there was anything strange about them, certainly not now. They are useful and happy - both found their niche and left the pressures of the outside world behind, while still being in the world.
Regarding money, they obviously don't pay rent and board but they earn their keep and parents give them an allowance.
Maybe your son will find his feet in a similar way, especially if he has no pressure. I do hope so.