CDL for buses converted into RVs?

In USA, do you need CDL to drive large buses with air brakes that are converted into RVs?

I think in the U.S.A. you could google that for an answer. However from what I know you don't need a CDL for personal use. However be careful going into U.S. Parks. They seem to have their own laws. As long as you have to RV or bus in your name.