It's quite easy to live for months (or longer) in a camper or 4x4, the longest I've gone is 3 months but once you can do a few days it's all pretty much the same.
Of course such a small vehicle cannot really carry food for months and we had to buy a lot from towns, but if you can hunt you could do it.
OK this isn't a trailer, but it could be there's no real difference. Total cost, maybe $2-3000 (if that) plus vehicle, including 2 fridges, mains power and solar.