I hope my post h.s.yeshiva boys stay learning for as long as possible–at least until they get married,if not longer.So long as they take it seriously,it refines them.
If a bochur isn’t learning “for real”,then the next-best “career choice” would be something in klei kodesh(ex.safrus, or being a rebbe for an age they are good with).
If neither full-time learning, nor the above type of jobs fit the young man, he should at least try to work in a POSITIVE SEVIVAH.