What is it that he is aiming to do?
I do't work in the field myself, but my DSis is a professional musician of 20 years so I've listened to her joys and woes over the last 20 years a lot....
He needs a really tight grip of admin. He will be freelance I imagine, so needs to know about IR35, invoicing, tax returns, allowable expenses, union rates if necessary etc, and keeping tight records. This is very important.
Sometimes at the start it is worth doing favours for free to get your name known. But not for too long.
Network like mad.
Set up groups yourself - yes, there is admin in this, but you get a fixers fee - she runs several groups, so doesn't always do the work but arranges and gets paid for that. Often she is in them too, but has a roster of people (still College contacts quite often, so he should hang on to his mates!). You also need good social media skills/web presence for this.
Teaching/tutoring is always a decent back up plan for income.
He will not be rich, but if he is savvy, he can do fine (and enjoy his work, which is worth its weight in gold) , but may need a diverse portfolio as said above.
This is from a musician perspective, but may still apply.