Freckles, I assume from your post that you want to add a recepticle in a place that does not have one provided for you. If you know what you are doing, the 120 volt is very doable. The cost would be low. If you don't know about electricity it's a job best left for someone that does. You would need to have a blank spot in your breaker panel, the correct wire, a GFI protected recepticle, box, cover plate and some tools. Again, you must know electrical wiring. Be sure to de-energize (unplug) the coach before touching anything.
Peace
Dave