I lived in the RV for 3 months while the house was being built. It was during the winter and they had the coldest December in 100 years - go figure. It was not cold by other standards but we woke up to 7 degrees a couple of days. It was below freezing for a few weeks.
We insulated the water line going into the coach. We built a box of rigid foam insulation for the filters and the water softener and hung a shop light in it. We just cut the sides and top from thick rigid foam and put it together using duct tape. It worked great! We ran the furnace and we had a heater in the living room and another one in the bedroom. We kept the coach around 64 degrees to save on propane but it was comfortable. We had a button to blow air into the basement and water area and made sure that was on. the coach has double pane windows and good insulation. We actually used less propane than almost everyone in the RV park.
It was not the most fun I have ever had but we made it through the cold spell just fine. If I didn't need to be there to watch the house building, I would have done like many others did and go further south.