Having read your edit explaining the temporary nature of your plan, I would offer a couple of observations. First, once you factor in the up front cost of the trailer, propane for heating and cooking, figuring out where to do laundry, etc. you may not save as much on living expenses as you might think. Can you live with a tiny fridge and a six gallon water heater? Will electrical service, water, and sewer be available on site?
Second, if you decide to do it, I'd look at used units, since I assume you'll want to sell it once your cabin is finished. You take a big depreciation hit when buying new, and the wear and tear of full time living will not help.
