Regarding modular homes: from what I've experienced (former licensed General Contractor), modular homes don't really save you a whole lot of money over a stick-built home. That is, if you put quality molding, materials, wiring, etc. in it. You just get it built faster in a controlled environment.
Personally, I'd rather have a mobile home (trailer we call 'em here in NC) or a tiny, minimalist Katrina-cottage style home than spend the money for a modular.
Gopher, how do you envision using your home? If you're considering a trailer, I'm guessing that you are not intending to host the local medical association surgeons regularly for dinner. If you want an efficient, well-built place to live and sleep, please look into one of the many minimalist style homes that can be built. It sounds like one would be perfect for dropping in the middle of 25 acres somewhere.