Ahh, something I'm familiar with!!
I did exactly this - bought a house and had it moved to my property last year. Best thing I've ever done.
I had quotes on building a 1,600 sq.ft. house on my property. Quotes started at $175,000 (up to $225,000!!). I found a 1,450 sq.ft. (single-story) house that needed to be moved (about 7 miles). The cost of the house itself *and* the move was $7,000 total.
The foundation cost $8,000 (this is the one thing I regret, I paid too much and was not particularly happy with it - but it's done). I'm very pleased with the house itself - it's very solid - all 3/4" tongue-and-groove southern pine paneling. I'm doing almost all of the renovation work myself. The final cost will be about a third of what it would have cost me to have something built and I'll have a much better house.
I highly recommend this approach, especially if you're handy and want to do much of the work yourself.
I did one other thing I would recommend. Home Depot sells 'storage' buildings. The biggest one is two-story, 18' x 32' but the one I bought was a bit smaller (two story, 16' x 24'). They did an excellent job - it's built from scratch, was up in a couple of days, they showed up when they said they would - I have nothing but good things to say about the whole thing. The price worked out to about $10/sq.ft. Then finish it off inside yourself. Evidently a lot of people are doing this for things like a lake house, etc.
Good luck in whatever you decide. Feel free to email if you have a specific questions about moving a house.