I would check out arctic fox. They make a four season trailer and they make toy haulers. I do not know if their toy haulers are also a four season trailer but this company has one of the best reputations for cold weather camping. That said, camping in -30 is not exactly a realistic plan. I'm not sure your heater will be able to keep up and if it can, I don't want to see your propane bill. I know their are tricks using incandescent light bulbs to help keep the basement warm. Remember you are at risk of a fire using a heater or incandescent light bulb for any length of time like you will need to do. I just can't see any way to prevent your lines from freezing up, even with heated tape. Good luck.