Several things you can do. 1st do you have a 4 season camper or a heated basement?
If you have a heated basement, then by running your propane heat you will keep your water lines from freezing. If you are not long term camping, then instead of purchasing heater cords and insulation for your hoses, fill your water tank and use that for water. Be sure to be sure it is sanitized or just use the water for all except drinking. Use bottled water instead. Be sure to keep your dump valves closed and if by chance the valves do freeze then thaw them with a hair dryer, so you can dump.
Camping in the cold, freezing temps can be done, but you have to be prepared.