Any chance that one of the outbuildings could be cleaned up and converted to living space? Even just one room? At least it'd get you out on the land (it does sound just wonderful!) Then you can insulate w/ straw bales, etc, etc.
Could you can hang out in the tent while you work on repairs, etc? If the owner is agreeable, maybe you can salvage what you need from the trailer or other buildings. I know someone that converted an ancient chicken coop to a rental!
Some ideas that may or may not work for you:
Can you borrow someone's camping trailer for a while?
Google 'van living', 'tiny houses', 'alternative housing', 'RV living', that kind of thing. There are some neat spaces that people have created.
What about a storage shed kit? Some are big enough to put a loft in it for a sleeping area.
Earthbag construction? Check out Kelly Hart for some ideas,
http://www.dreamgreenhomes.com/ All you need is something to keep the weather off your head, the rest can come a step at a time if you're tough enough, and I think you are!

I love doing things on the cheap, and having them look really good by the time it's done! I love your idea of the li'l market, too.
Hit your local FreeCycle. Maybe someone has an old camper shell they want to get rid of. And by all means, let people know what you need...ask! You might get a freebie something or other that works. (Cheap is good, free is better!)
I thought in most areas the power company would get you hooked to their services up for nothing...not in some really remote locations, but was there power out there at some point? The last time my computer was in the shop for a week, I had to think to remember what in the heck I used to do before I had it! LOL