I live out by Spokane and I saw a sign at the real estate place on Hwy 160 the other day. I think it was 10 acres for 35,000 but around here God only knows if the acrage is anything you could build on without a lot of work. Our land was a little over 3K per acre but out of 7 acres I really only have 2-3 you can use. My back yard drops 100 feet and back up that much before the back of the property, so I've only been down to the pond in the bottom less than a dozen times in the three years I have lived here because it is a bi-atch of a hike. I've been thinking about trying to clear out a trail to take the jeep down, though...
All that said, if you want 10 decent acres you are probably going to look at somewhere in the neighborhood of 60K. Then pick your school district and start looking from there. Stone county aroud Hootentown is probably a good place to find some bargains if you are OK with the Galena school district. We chose Spokane because we know a lot of people around here and were able to build in the middle of nowhere, but still be close enough to the unincorporated town of Spokane that we can get DSL and Cable.
Also, if you are looking, keep taxes in mind. Christian county is going to be the highest, and Taney the lowest. (because of the tourism tax income)
Good luck!