I think this is one of those things that varies a lot between states. Plumbing apprenticeships in PA, at least, are four-five year programs that require an ent

I think this is one of those things that varies a lot between states. Plumbing apprenticeships in PA, at least, are four-five year programs that require an entrance examination, high-school diploma or equivalent, and a mix of on-job and in classroom training before you're allowed to take the examination to become a journeyman (that is, legally operate without supervision). Source: I have an uncle who owns a plumbing company and a cousin who's going through an apprenticeship.