Yes, for example Rich "Ace" Franklin was a teacher. Kenny "Ken-Flo" Florian is an announcer as well as Frank Mir. But like the others said before me, if they are not widely known or popular with no sponsors then they will have another job.
BEcause they have to pay for gym membership, training gear, managers, training facilities, etc. But if they do have sponsors then they usually dont have another job and they use their time to train more instead.