Even RV's well prepared for winter weather are not all that great against the cold due to the thickness (or lack thereof) of the walls, floors and ceiling.
No matter which brand/make you choose, you will need to take extra measures to insulate it. Skirting around the bottom helps a lot, but it should have some insulative qualities as well. I'm sure there are those with experience that can offer more than I can, but having done some winter camping I know that by itself and without additional measures, any RV, TT, or 5r will not be as comfy as you might prefer without a substantial amount of heat generated inside. Propane will be used up rather quickly and an electric heater will be working overtime just to keep up in weather like Colorado experiences during the winter months.
