For anyone with a work ethic but more time than money, an earthship is a stunningly efficient passive home designed in the 70s that uses rammed earth tires covered with adobe as walls, thermal mass to maintain heat, and giant windows to bring in light. The roof is designed to drain into water cisterns, and grey water (kitchen, bathroom sink) is used to water crops grown inside a beautiful inner garden. Its fully ready to be integrated with PV.

Here's an example if you want to see one of the many that people have built. Here is some more analysis of the viability.