Cold weather requires some actions to take before leaving your RV for days at a time. You have to worry about anything with water in it freezing. Most RVers will unhook the freshwater hose drain it, blow out any remaining water and store it in a compartment until they return. Same thing at night if freezing temps are expected or you can wrap the hose with a heating tape.
Buy an RV with heated freshwater and holding tanks or have heating elements added.
I've read that many folks will leave a low wattage incandescent light bulb on inside the RV or a couple for a larger RV. This seems to provide enough heat to keep things from freezing inside when they are away. A thermostat equipped portable heater will also work but there may be a fire risk with an unattended heater.
Good luck with your new adventure.