Don't know of any way of telling how many miles are on a TT unless it was a rental with a meter to measure the miles. A old one could have been towed on short trips and have very few miles and a new one could have belonged to a fulltimer and been all over the country. Just look at the overall condition, tires, frame,axles,and outer skin. Probe around coners and in the floor for soft spots and be leary of any that show sings of leaks. I agree "there is no such thing as a stupid question". If you don't know ask.