Given the economic collapse we are experiencing in the US, with huge job losses and more and more people losing their homes, there is a need for information about alternative, very low cost temporary and permanent shelter.
With a few tools, a bit of land (which could be cooperatively owned) and a serious attitude shift about what is desirable and acceptable in housing, wonderful shelter can be built for not a lot of money. Consider the yurt —
A yurt is (traditionally) a portable shelter used by nomadic people in Mongolia and other regions. In its original form, it consists of circular, tightly bound lattice walls with a wool felt covering. Roofing is constructed with poles attached to the lattice at the outside edges and a circular ring in the center. The interior space is entirely open, with no load-bearing partitions.
There are hundreds of variations on this basic plan, and dozens of US yurt builders —
Red Sky Shelters portable "Yome"
Laurel Nest Yurts
Blue Ridge Yurts
Although these may look like tents, they are fully capable of withstanding serious weather conditions and can be used year-around in most climates. If you wanted something more "solid" and super-insulated, there are new, innovative prefab construction techniques and kits available —
ICS Solargon, made with SIPS (structural insulated panels)
Smiling Woods panelized yurts
You can buy plans, parts kits, completed kits. It's entirely conceivable that a family of three could live in a 20' yurt (about 310 square feet) with a basic cost of about $8,000. With variations like straw bale or earthship walls, the cost could be even less.
The links above are just a sampling of what's available. The best overall source of information on yurts is here.