In addition to the Arctic Pac waste tank heating pads, you would need the furnace running to heat the water pump and water filter bay, as well as possibly heating the dump valves, if there is any liquid in tanks. You would also need heat in the living area if your fresh water tank is perhaps under the bed or elsewhere above the floor.
You could theoretically put a space heater in the basement water compartment but it probably need to be low wattage, and you would need to install an electrical outlet to power the heater.
Blowing the lines out with compressed air, emptying the water heater, and putting antifreeze in the drain traps would be a better idea.
2020 Sunseeker 2440DS on 2019 Ford E-450, Trekker cap, Topaz paint