We have a 1998 Lance Lite 165-s xcab that we bought in 2001. These don’t have much insulation unless ordered with a winter package, which were very few and far between.
The best I can do in weather below about 22 degrees is to run the camper dry. No water in the water or grey tank and no running water. All tanks and water systems drained thoroughly including blowing compressed air through the lower reaches of the water pump. A few gallons on hand of minus 50 degrees RV antifreeze miserly poured directly into the toilet after each use as a flush. A lot of sturdy gallon and litre jugs of water placed in that floor cabinet near the door. With all the weight of the water pushing on the cabinet latch, I had to add another mechanical exterior latch to keep the jugs in place. 24-48, 16 oz bottles of water stored behind those little doors under the sink and fridge at floor level. An insulation job in all vents and behind cabinets. I used 1-inch molded R-11, foil faced, both sides closed cell foam cut to fit and glued to the walls behind the cabinets. Install at least 200 watts of solar on the roof. replace all 12v incandescent bulbs (12 on the interior) with LED’s which take only 1/10th the amps. All these upgrades do not equal a real 4-season camper, but allow you to survive without running the heater all night. Another winter item is a rubber floor anti slip mat under a cut-to-fit piece of pile carpet. This saves your tootsies day or night during winter months.
We turn the heater off in the night snug under a high pile goose down comforter and actually use sheets and blankets, which is nice. In the AM i get up and heat water for coffee and turn on the furnace once again. The total volume is so small, just the heating of water helps, with the caveat of opening a close top vent and cracking a window to let the water vapor out.
My biggest complaint about the Lance Lite is the lack of sufficient insulation.
You’ve got your work cut out for you.
2020 Ford F-350 XLT FX4 4WD SRW SB SC 7.3L Godzilla Gas TorqShift 10R140 397 amps dual Alt dual batts Frnt Dana 60; Rr Dana M275 E-locker 4.30's 4580/4320/4066# payload 7243# curb wt. 11,300# GVWR 5-er prepped. 2020 Northstar Laredo SC, 12v compressor fridge, cassette, 320w Solar sub zero insulation.