The big question would be as to how much of an investment you need to make to be well equipped with everything you need to make most repairs, as well has have an inventory of most often needed parts. Then, can you carry any overhead until you've built a reputation and network of campground owners that will recommend you to campers looking for a technician. In some areas, you may be in competition with techs that already provide mobile service. I used to live near a tech in Newfane, NY that had an independent shop and also did mobile work (RV Mobile....John...great guy!). If you decide to do it, you need to have some good advertising handouts that campground owners will keep on display and handy, and really try to establish a reputation through campground owners. Good luck!