In the last 7 years we have never (to our knowledge) gotten a mouse in our RV. We have not seen a mouse or signs of a mouse. Biggest danger is an rv that sits idle for periods of time and gives them time to investigate the available condo with free rent. If you are going to let it sit then I would think putting moth balls around anything that touches the ground would be a good place to start. The problem with putting poison in the rv is where they will die.

I have heard that if you put cayenne pepper around openings, that will keep them out. That is if the opening that they are getting is amoung the ones you coat with pepper.

Mice and Ants, given enough time you will deal with both.  We full-timed for three years before either got in and we have now dealt with both.  Ants can come through the smallest holes, a tiny gap in a slide gasket can let them in.  Mice can squeeze through a hole smaller than an dime.

I'm knocking on wood but in 3 plus years of fulltiming we've not had mice. BUT we've had ants! ...looking for water they say. Best way to get rid of them we've found is to sprinkle ant killer powder around any thing touching the ground--wheels, sewer hose, electric cord etc. Then we put those little black ant houses inside in strategic spots. No ants for a year. BUT we have been carrying around ladybugs for a couple of years. I think they hibernate then pop up for a little life then sleep...or are they reproducing somewhere inside. In Iowa two years ago we were caught in a swarm of the critters and they've never completely left. They are the new kind that like to bite to let you know they're around. We  just consider that we're giving them a ride now...no problem!

To get rid of the ants - sprinkle a little cornmeal where you see the ants - they will eat it and blow up - no more ants....hard to believe this really works -- its kinda like the soap in the bed trick to prevent leg cramps. 

We put moth balls (two or three) on the top of each tire, when we are parked for extended periods of time, and have not had a mouse at all !  I was told by a vet friend that mice have sensitive noses and the smell from the moth balls should discourage their climb up the tires, which is the most common way they enter the rigs.