Second, that's a nice picture but doesn't have any relevance to living in the desert. No green houses needed. What you need is lots of shade cloth.

And the houses need to protected from the sun and have a large thermal mass to absorb the cool of night.

Third, the desert really isn't cheap.
There is lots of great land that is relatively inexpensive.
The real cost is in that of infrastructure.

I do like the idea of creating permaculture small group living units.
However, you need to go two or three steps beyond what you have pictured above. Its all out there. Just got to bring all the parts together.

Things like compressed earth building blocks (like adobe) are really great for getting those structures you need built fast, quick and cheaply.

Check out my post on underground greenhouses.

And, I will have more on real solutions for actually doing this project, stay in touch.