The quick cabin - most likely the most economical shelter building kit available - with simple pipe or 2x4 or 2x6 lumber you can build a small cabin that will sleep about 6 people, close quarters but with insulation and a small inexpensive wood stove.
The system is quite easy to use and several cabins can be built for the cost of a single pre-built.
The Eco-Cabin blog
Lodge-Tech has even turned it into a geodesic/yurt kit.
Check out the wooded seclusion yurt.
Stromberg’s Starplate systems