These earth buildings are cool in the summer, warm in the winter, and because of the domed shape, highly earthquake resistant. They are simple and inexpensive to make (like making an igloo out of bags of dirt instead of packed snow - I live in snow country). You could use burlap bags instead of the tubes....

Have you checked Craigs List for used yurts? When I lived in Oregon, I would see used ones in the paper fairly often. Pacific Yurts makes good ones: www.yurts.com/default.aspx

Best of luck to you!
~Pippi