First I notice that you are in Wisconsin or cold as hell. Good for you!
You don't need a trailer. If that is all you have, insulate it real good.
Do you clean mostly residential, apartments, commercial, or a mix?
Do you work mostly alone, or do you have help?
Do you clean tile and grout and rugs?
Not to get too personal, but are you wanting to pay cash for the machine or finance something?
Answer these first.
For me I could never buy a new single wand machine. I make way more money faster when I have two tools going. A big machine can do small jobs single wanding great and do the bigger jobs even better.
If you are getting a heat exchange machine, you will want to get a real dual wand slide in machine.
If you are working alone and need the great heat in winter, then a propane machine make sense.
What is your budget.
By the way portys suck and should only be used as a last resort.