I would not spend a Midwest winter in a 5th wheel or any other camper. Period. I lived in Iowa for many years and experienced -20 and more too many times to count. This is real OMG cold weather. And yes, I see where you are now.
Unlike most all houses, these rigs are not nearly air tight. And when the wind blows, you will know it.
There is a huge difference between 32 degrees and zero degrees and there is a HUGE difference between zero degrees and -20. I can tell you from experience that after it's been -20 for a while and it warms up to zero, you feel like it's shorts and t-shirt weather.
One of the problems is that you have 2 ft of air under the bottom of the rig. That air will be -20 too, even if you skirt it. That problem does not exist with a house.
Your propane furnace will never shut off and it will cost a fortune for the gas it will use. I suspect a bottle of gas will last way, way less then a week. Same for any electric alternative - I doubt you will save any money by heating with electric in this extreme of a situation - that is why homeowners in the northern states have a natural gas furnace - nobody heats with electric unless there is no other solution. I knew people that lived out of town and heated with propane. They dreaded the winter bills.
And before I get jumped on, I know many of us (including me) use electric heat in the winter, but that's because we're in much more moderate climates (AZ, TX, FL). I think the math works better when you have nice sunny days and only moderately cold (cool ?) nights and can go easy on the electric heaters. But I can't believe it would be a cost effective solution in climates that experience real no kidding cold weather accompanied by lots of cold cloudy days.
It will be cheaper (and warmer)for you to rent an apartment.
I have a 2014 Bighorn with the Yeti package and it works well, but these rigs just do not have the insulation of a sticks and bricks house.
Tim
