As Carl the Painter mentioned, it'll probably be a good idea to see what your state's laws are. To be legit you may need to get your Painting contractors licence. Then on top of that you may need to be bonded and insured. If those things are required in your state and you haven't done those things you could be asking for trouble. Not only from the contractors board, but if a savy client realizes that you're not licenced, they don't have to pay you a dime for any work you've done. All it would take is one or two pissed off clients to make your life start to suck.
I'm not trying to discourage you, but there's way more to a paint business than you might think at this point.
Good luck!!!