I was looking at a used f250, and was almost set on it, until I looked at the floor behind the drivers seat and saw mouse remnants. I closed the door and never looked back. As mentioned, they love insulation, and if one gets in, then almost guaranteed dozens will have been in there. I live out in the country and battle with mice in the house all the time, even with cats, they can be a PITA to get rid of.
When I store the trailer I use a lot of mothballs all around the trailer, which seemed to have worked well as I had no indications of mice anywhere, and also in my workshop, I had mice get into some of my RC planes and eat the wood, heck I still have chunks of dog food in one of my planes. Last year, did the mothball thing around all my planes and no more mouse issues.