@SoTiredNeedHoliday
Something I suppose would help him would be to think about the last few years and identify things he has done which have meant being busy but which were also enjoyable.
I've tried to phrase it in that way to take into account the fact that there are so many ways of being employed. If I sit and think about the people I know now and the people I've met in my life, I realise what a vast range of jobs they all did.
Quite a few have gone down the academic route and spend their days in professions such as the law or medicine; a large number do very different things, though, such as leading outward bound courses for young people or working as support workers.
One friend of mine is a chef; he started out at the age of 16 by asking for work in a hotel kitchen.
When you think about things which your son has enjoyed doing, can you identify something in particular? It might not be a traditional academic subject - he could have different skills, one for a sport or an aspect of the arts - what does he enjoy?
If he sits and thinks about what he enjoys, he may then be able to think about how he can turn that into a kind of paid work which will allow him to be financially independent.