Since “earth” is a less than informative location and you don’t say where you are or where you think you might want to go it’s tough to give you a good answer, but, I’ll try.
First off, do NOT use water from the RV’s plumbing system. It will not end well. Flush and cook with jugs of water, the black & grey tank dump valves are big enough to be the last things to freeze.
Secondly, do not forget that RV furnaces are HUNGRY. Both in terms of propane AND electricity. A single day with heat on will kill your battery, I said “day” not “night”. A weekend parked with heat on and plugged in will put a serious dent in a tank of propane.