Shop Heat

Run LP then.

If you aren't there often, that would make me want a larger heater even more as it needs to bring the temps up from outdoor temp. It's not coming up and then maintaining.

You are right.
I searched CL but came up empty on a used mobile home one. I was considering this, but the immediate funds aren't available, you have to add a vent kit ($309) and it says it only runs at 81% efficiency with LP. Not sure if that matters or not.

Add all of that together and I am looking at at least $1000 with a 100Lb tank of propane. Which I am not opposed to spending, I just can't afford that right now.