I'm at work so can't dig up any sources atm, but I would point you in the direction of some of the economic reforms of Diocletian. One of the things he did, mostly as a means to keep the legions staffed, was to make jobs hereditary. If your father was a soldier, so were you. Father, a baker? There you go. He did this by creating guilds that took over many professions. Prior to this point in the history if the empire the economy was much more a slave economy where workers would, generally, have had little choice in career.