American Ingenuity has prefab domes. http://www.aidomes.com/ Not cheap, but their construction methods look a lot better than other dome kits out there. The panels, once installed, are the roof/insulation/inside wall. That means in, say, two weeks you can have everything done except the inside finishing and mechanical.
Timberline Geodesics http://www.domehome.com/ has less expensive kits, but they are wood. That's not necessarily a bad thing, as long as you are aware that due to the different shapes and angles involved it takes a real pro to roof it properly to prevent leaks. What you might save in kit costs comes back in roofing.
The biggest problem I can see with one of those is that banks typically are not bonkers about financing unusual houses. The reason is that if there is a default the bank will have a hard time unloading it since it's not the typical suburban cookie cutter house.
You might also look around for one of those 'house for a dollar' deals. Here's how it works: someone buys a piece of property with an existing house on it. For whatever reason, they don't need the house. So they sell it for a dollar, but the catch is you have to move the house by such and such a date. That takes a fair amount of planning. There was an article in the Mother Earth News about a guy who did this, he marked every board in the house with a coded number that said where it went. He then disassembled the house board by board and reassembled it on his property. That was obviously a very time intensive project, IIRC it took him about two years working on it every day.
Another angle you might consider: contract someone to 'dry in' a house for you. They build the foundation and exterior walls, then put the roof and doors in. You now have a dry box which you then finish out as you get time. Again, banks aren't bonkers about this since if it defaults they are stuck with an unfinished house.