It's time to winterize...

^^^ Good explanation Rick, there are misconceptions about what GFCIs do and don't do. To the OP, I don't see any concerns using a space heater in a motorhome as long as everything is up to par, and with a 30 amp service it likely is. It's no more likely to cause a fire than using a space heater in your house. I don't know what happened in your cousin's case, but in my more than a few years in the fire service, most space heater fires are caused by items too close to the heater. Sometimes they cause issues if there is faulty wiring due to the high current draw (actually happened to me in my house), but if your wiring is good you should be fine using a space heater.