I too live in an uninsulated (and very old) motorhome in the mountains of the Pacific Northwest. Temps dropped to 16 degrees F last night. No working furnace. I don't use the plumbing in my RV at all, no running water. I'm used to it, no big deal--and now worries about pipes bursting from hard freezes.
As emergency measure, turn off your water,drain all the pipes in your motorhome, leave them dry. Get or buy a few of those gallon jugs of water. 4 gallons for a week is more than enough. That's your drinking water. If the RV has a built-in water tank, drain that, too.
Get one of those five gallon plastic buckets with the lids and handles on them--the kind paint often comes from. Home Depot sells 'em, empty and clean. Fill it with water from your tap--the other end of that outdoor garden house. That's your bath water. Keep it inside your RV so it doesn't freeze. Heat up the water on your oven in a pot so you have nice hot water to bathe with--though the heating takes a while. Sponge bath to minimize use of water. That bucket is also your dish washing and cleaning water. Refill as needed.
Heat...I have two portable electric space heaters, both bought from the thrift shop, used. Both kept in my bedroom. Both kept at half-power so the AC plugs don't overheat and melt or burn. That warms up my bedroom about 20 degrees from outside temperature. So with it 20 degrees outside, it's 40 degrees inside. Yes, brrr.
To supplement with additional heating, I have an indoor-safe propane heater. Mr. Buddy Portable Buddy heater, plus a Mr. Buddy propane hose (10 feet long) a filter for the hose, and an external 20-gallon propane tank (common standard size). I keep the tank outside, run the hose from it through an opening in my RV to the heater in my bedroom, warm radiant heat.
If you can't find a Mr. Buddy locally, eBay and Amazon both sell them. Walmart too, I think, on their online site. Home Depot usually has several models of propane heaters but most of them are for outdoor use only, for building contractor worksites (and they put out massive heat with massive propane consumption to match), not indoor-safe. Two models of Mr. Buddy, both work very well.
I only need the propane heater for a week or two each year.
So I've got 3 heaters going. I don't use a third electric heater because I only have 15 amps power--not enough to power a third heater. Hence the propane heater.
I have two thick high quality sleeping bags (both rated warm down to 20 degrees), several layers of sweaters, thick winter jacket. I'm comfortable. Thrift shop often has (poor quality) sleeping bags and blankets that you can put over the windows to lower heat loss, quite cheap.
This cold snap should be over very soon, within 2 or 3 days. You just have to endure until then.
In an emergency, hopefully you have a working vehicle with a working heater...and you can drive to a mall or library or 24-hour supermarket so you can be indoors and warm. I used to do that in my homeless days, years ago.
I live alone too, and am very low income of $670 a month. So everything is adapted for maximum comfort at very little cost. If I can live comfortably and happily through a Pacific Northwest winter on that little money, so can you. I love my present life, love where I live. :) I'm a happy guy.
If you ever feel lonely, just want to talk, feel free to PM me any time. We live similar lifestyles it seems. Perhaps I can help with advice, tips, or just offer moral support. Need a friend?