We spent two Montana winters in RVs; once in a class A motorhome, and once in a fifth wheel.
Both times, I built the water line out of hard copper tubing, heat taped and insulated. No freeze-ups.
The sewer line I did not heat or insulate. Leaving the grey water valve open seemed to keep it from freezing, probably due to all the hot water that went down the drains. Of course, I opened the black water valve only when it was necessary to dump the tank.
When we were in the Class A, I bought a 100 pound propane cylinder, and the necessary fittings to hook it to the coach. It worked much better than the onboard tank.
In the fifth wheel, I rented an 80 GALLON tank, hooked it up, and the propane company kept it full all winter. MUCH better!
In the motorhome, I bought a 100 foot roll of 4 foot wide Reflectix insulation and wrapped it all the way around the coach as skirting, as well as covering the grille and windshield with it. It helped greatly. There was a draft around the door, so we got a blanket from a thrift store and made a drape out of it to hang inside the door. There are "pillows" available to push into the roof vents to insulate them.
As stated, be careful of electric heaters. You really NEED the warm air from the furnace circulating in the RV.
Also, if you yield to temptation and get a propane catalytic heater, be sure to read the safety instructions and warnings! Failure to properly ventilate the RV when using one of those heaters could KILL you!
THINK and Plan Ahead, and your winter will not be a problem.
