Look at poured earth.
http://www.michaelfrerking.com/index.php http://www.ehow.com/how_2140534_build-house-from-poured-earth.html http://www.greenhomebuilding.com/poured_earth.htm Use clay from your land, flyash (recycling an industrial waste product) and some cement. Poured earth can be the above-ground part of a partially-underground house. Make ONE form - square, rectangular, round, oval, spiral, and use it over and over to add rooms, right away or in the future. Our design uses a golden mean spiral wooden form
http://www.soulsofdistortion.nl/images/picture%2025.gif http://www.floweroflife.org/spiral01.htm designed by Michael Frerking that can be poured, then flipped to pour a spiral in the opposite direction, then flipped two more times to make four spirals that surround a small square center for the kitchen. Building the square involves one more small straight wall form that is used four times for the four connecting walls. Walls are 24 to 36 inches thick, depending on whether you want it to last 500 years or 1000 years.
As advised above, build the form, pour one room (one of ours is 900 square feet), live in it and learn from it, then pour another room if needed (eg, growing kids) as time and funds become available. The expression is "dirt cheap" for a reason!
