I looked this dealer up (Best Pre-Owned Rv's). The wording is just advertising, doesn't mean that they're the best, just means they are trying to get your attention, and it worked.
After looking at their website (or what they considered a website), they had a total of 17 RVs listed, so perhaps this is a new (just opened) dealership. If you're investing your retirement money, then spend longer hours doing research to educated your self with each motor home you're considering along with the dealership... Stay away from Camping World.
