You're misreading what I posted. Doctors, CPA's (accountants don't fall in this realm), and teachers need certain certification by states. Interestingly, anyone can be an accountant. There is no state certification to be an accountant, and I know several people who are in the accounting/finance field who do not have a degree in such. Social Service worker, Caseworker, teachers are all state/federal jobs. So, yes, they have certain requirements. But, you can be a plumber's apprentice right out of HS without a certification, same goes with a journeyman, and accountants/bookkeepers, managers, etc, etc. There are no age, education or licensing requirements. There may be business requirements, but those aren't directly on age, they're on experience (as you pointed out). NBA's rules are specifically around age (I would even argue, illegally). 18 year old basketball phenoms have plenty of experience.