TT for use year round in temps above 20F

"Four season trailers with enclosed tanks are really expensive."

Winnebago's Minnie line four season TTs are not expensive.

If it is stationary most the time but insulated skirting under it. That is what people that live in cold climates do all the time. Add heat tape to the plumbing.

People make such a big deal out of camping the cold. Plenty of people live in them full time at below zero temperatures all over the WEst.

Wife and I camp year around and in below freezing temps in our 4 season trailer.

Here are a few considerations:

No trailer is 4 season when unoccupied for long periods or should I say unattended.
Furnace must be set and Propane consumption monitored.

Boondocking in freezing temps require continuous use of generator as furnace drains battery in a matter of hours.

Camping at a campground with electric hook-up is very doable in freezing temps.
We set furnace at 70*, always have 2 bottles of propane and outside shower is drained and off.
I still winterize after a trip,takes 15 minutes and less than 2 gallons of RV antifreeze.

I see boondocking for extended periods in 20* asking for trouble.