Re: Building a Greenhouse
I like the idea of a 6x6 perimeter frame; half-lap the corners and spike together. Sit the perimeter of good gravel fill for a foundation. I don't know about your climate, but I'm on the east coast, and I'd put in a floor drain; in your situation, excess water could evaporate on contact with the brick, being as dry as AZ is reputed to be.
I'd think that a compacted stone dust base would be fine.
You may want vents at the base and at the peak, and some shade cloth to avoid the solar kiln effect. In the winter you could if needed, bank the foundation with straw bales and tarps to keep the floor as warm as possible for as long as possible.
I had a greenhouse at my disposal for a couple of years; it's such a great tool to have you won't know how you managed w/o one, and if you lose it (as I did when I moved) you'll miss it.
Remove not the ancient landmark, which your fathers have set.