Everyone has a winter story so here is my in a 97 LY diesel pusher. I got a job transfer to Montana in October so lived in the Airstream for about 6 weeks till I found a house in Great Falls.
First is to understand where your water and holding tanks are located. On gas models the fresh water tank is usually under the bed. On diesel models is outside midway between the frame rails behind the diesel tank. Both holding tanks are behind that closer to the area under the stove and toilet. The furnace heats both holding tanks so always make sure it functions properly, especially at night. Its very noticeable because the bath floor will be warm to the touch.
Due to issues with water hoses on city water lines freezing, I decided to keep my water tank full and use onboard pump. Problem I had first occurred over Thanksgiving weekend when the temps dropped below 0. Morning after found my freshwater tank had frozen and nothing but a drop coming out of faucets. Used bottle water for drinking cooking and filled some liter bottles at the laundry to use in toilet when flushing. Took about 3 days for it to thaw out but everything went back to normal once temps got up to 40. No internal damages. With temps that cold, make sure to keep cabinet doors under sinks open so warm air circulates. Both my roof units have electric heat so in daytime would switch to them and save the propane. Had I stayed on the Airstream through winter it would have helped to enclose the exterior base with insulation board and put a light into the sewer compartment to keep drain handles from freezing.
Winter living in any RV up north can be an experience. Live and learn.....it can be fun but expensive too!!