Earth-cooled, shipping container underground CA home built for 30K

As a kid Steve Rees played in caves and learned how the earth could cool. As an adult, he buried two shipping containers and created an off-grid retirement home for himself and his wife Shirley. After a few years of camping on their 10 acre plot in Northern California, they bought two shipping containers, hired an excavator and got to work. Doing most of the work themselves, their finished home cost them $30,000 (solar included). Their 640-square-foot space cost them less than $50 per square foot. Rees e