In reply to tripp:
For those who might want something other than the cheapest build possible and don't mind some simple D.I.Y. work you might look into I.C.F.s. (Insulated Concrete forms) I've built with them and can tell you they make working with concrete almost too simple..
They are big foam blocks that go together like giant Leggo's. I made sure the ones I bought were protected against insects and rodents. I forget what they use but if something were to get past the sealant there is something in the foam that kills them before they can infest the foam. Mine came with a nice video and complete instructions.. Plus the required bracing/scaffolding needed. The place I got them from worked from my sketch of what I wanted to achieve and sent me the exact number of blocks I needed in exactly the configuration they had to be. I also bought the rebar from them and the tie wrap tool that made wire tying fun rather than complicated..
For window and door openings I went to a local sawmill and bought white oak and wrapped them in plastic for rot protection.. Since it was rough and green, at the mill I only paid 40 cents per bd. ft.
I started work on my project and in one day had the first two levels done with some corners up to full height. However I went to a race that weekend and so badly wrenched my back I was bedridden for over three weeks.. Since winter was coming on I put out a call for some help. I got my 14 year old daughter and 30 year old sister-in-law. Needless to say absolutely no construction experience at all.
They watched the video and in one weekend finished up everything.. On Monday the Building inspector checked everything and signed off without a single issue.. My wife got two young men at the local grocery store (Bag Boys) to aide in the pour when the pump guy came on Wednesday morning (again no experience) but I did get the guy who sold me the forms to show up and supervise the pour.
Everyone one arrived Wednesday morning ate the rolls and coffee and the pour went off without a single hitch..by 10:30 they had nearly finished up and everyone was gone by 11:00
The medication finally started to work and I saw the finished project for the first time on Thursday. The Bag boys and my daughter took down the bracing and scaffolding that weekend and loaded my truck and trailer to return to the place I bought the forms from (along with the rebar bender, and vibrator pump)
Sheetrocking the inside walls was almost too simple.. There are nylon strips to screw into every 4 inches but before I did I put wire in conduit to bury it. I used an old dull router bit to tunnel chase's in for the conduit and boxes and except for filling the shop vac with foam beads and the mess of getting them out of my hair that went off pretty quickly too. Since much of the outside was buried when I back filled I coated all of the blocks with a sealant.
The front I put brick tabs on for the stone I used to veneer the foams but I could have stucco'ed it or used that Dryviet stuff that looks like stucco if I'd want to save some money.. You could also put wood or aluminum/plastic siding up if you prefer.
Like I said it's not the cheapest way to build but it sure was simple.. It has a great fire rating since concrete can't burn. (use fire rated sheetrock for the best rating) massively stronger than typical stick (2X4, 2X6 ) building, In case you suffer from Tornado's or earthquakes. And a great R value.. Because of the thermal mass involved it's actually higher than it's rated.