Hey Graham,
I'm in a similar boat - sorely tempted by the cheap land (West Texas in my case at around $1K USD per acre; around 11 inches of annual rainfall) and inspired by the Greening the Desert videos I've seen.
From what I've learned, the way I would approach this is to think in phases instead of trying to rehabilitate the entire property at once. My Phase 1 would start with Zones 0 and 1, which would probably be up to a half-acre in size.
The first focus would be to set up systems for water catchment and irrigation earthworks + drip systems. I'd set my highest priority to capture and recycle every ounce of water falling on or consumed by all life in those zones - rainwater, greywater, all of it. I'd also want to put up windbreaks using desert plants - mesquite, creosote bush, yuccas, agaves, and prickly pear - on the windward sides of these zones to help counteract some of the evaporation effects.
Then I think I'd have to focus on increasing fertility directly in my growing beds - maybe in raised/container beds or the sunken beds similar to Lawson's at the Dead Sea project. Realistically, the first year or two I'd probably have to pay to ship in offsite resources - water and mulch material at least, maybe manure as well - to kick-start fertility. I'd get some rabbits and chickens going as well for their manure production as much as their food value.
If I do anything in Zone 2 during Phase 1, it would be focused on putting in the earthworks needed and defining a drought-tolerant cover crop polyculture planted directly in the swales and along keylines. I'd probably let that run for at least a couple of years to build up some fertility before starting the food forest crops there. My approach to Zones 2 and beyond would be heavily influenced by Mark Shepard's ideas about restoration agriculture.
This is all a pipe dream for me right now, but it has definitely captured my imagination. Glad to see I'm not the only one crazy enough to even think about trying this.
Good luck! I hope to hear updates on what you're accomplishing!
Be well,
Nate
