Water lines & tanks are definately the biggest concern, after that there is the concern of keeping warm without useing 100's of pounds of propane. Be forewarned a 20lb bottle of propane may not give full service in extreme cold. We had 20lb bottles only give us about 1/4 the service due to the pressure dropping from the cold, below 28'F.
We try not to winter camp in cold climates. However we still get cold weather where we are & we place sleeping bags & other warm blackets or pillows in areas that are not sealed very well. One of those places is the dash board. We drape the sleeping bags over the dash to the floor. You would be surprised how clod it is under the sleeping bags. We place our self inflating sleeping pads agaist the walls. Every little bit helps.
Dan Sees, Full Timing in the MH & Part timing in a S&B In Hampstead, NC
2013 Winnebago Journey 42e, 2014 Featherlite Car Hauler 3110 17.5', 2008 Mazda MX5,
2008 Toyota FJ Cruiser