It’s a great time to get into commercial aviation. I have flown with many younger chaps over the last 5 years who took the cadetship EasyJet route and not a single one of them regret it despite the debt.
I’d tell your son to 1) get a PPL and 2)get a subscription to Flight Intl, it’s the trade rag.
The ppl will cost c.5k. The instructor and school will know within a few lessons if he has the aptitude for commercial training. It’s fairly crazy imho to embark on commercial flying training having never operated an aircraft of some sort.
Also would advise finishing the degree. Nothing is a certain in aviation.