I wintered with a 5th Wheel toy hauler in Montana. I had to skirt it with 2” foam board and apply heat tape to the water source. It's not hard if you research and take precautions.
By the way, that region gets some serious cold snaps, but the Chinook winds blow through and warm things up periodically. A Canadian once told me that Vancouver has citrus groves. There's a reason they had to provide snow for the Olympic Games and it wasn't “Global Warming.”
Did that 5th Wheel have a "basement" as many do? With the piping past the water inlet enclosed. Many today even have heating in that basement.
A southern style FEMA trailer will most the plumbing and tanks exposed underneath is a different problem in a North Dakota winter.