Correct on flooring yourself, no permit required. But I don't have the time, or patients to do so myself, not to mention the wife's two-cents every 30 minutes - "you're not doing it right! That's not how they do it on TV!" GAWD ALL MIGHTY!
If you hire a contractor then he is going to go to regional building and file the permit because if he hits a gas line, electrical cable, or water line he wants to be able to tell his insurance that he checked the blueprints and it wasn't suppose to be there. That's why you pay more to have it done right, and professionally. I am not saying it couldn't be professional by a DIY person, but that's not me.