The key to your plan is to buy a condemned single wide and land as far out in the country as possible. Demo the trailer and then use the services water, electric, and sewer. Just make sure that you certify the well and septic prior to purchase. You will be subject to county inspections on what you use the land for.
To reiterate for OP "unrestricted" just means you can go residential, commercial or agricultural
(ETA - The other possibility as Utclmjmpr, says it could also be federal and that's a whole nuther kettle of fish. Although I wonder how much federal land gets sold to someone that isn't drilling, fracking or running a pipeline ;-)
I did almost what OldGator did but It was exactly what BobTop described. My property is Ag1(?) and outside city limits - less bureaucracy on what you want to do but...
Once you decide to do something with it there are county rules and permits.
My property was a collapsed 60 MH. There was a dead well and a septic tank and city power had been run in there but nothing hooked up for about 15 years.
I paid $6k for a new well, about $200 to have the septic pumped out and about $300 to have power hooked up, simply because I had to have a new meter box that met current code. I also put in a 50amp RV service for the RV.
I had another $500 or so in trenching and running buried 240V for the well pump. Another $500 or so to dig up, replace, relocate and fix the 4 inch sewer piping. Maybe another $500 in 1 1/2 inch water piping and trenching and faucets.
I had planned only to live in my RV but I decided later to install a 1700sq/ft mobile home. This required about $800-$1000 in trenching and buried 4 wire cable.
Note that in my County the "owner" can act as his own contractor on everything so I did all my own work, ensuring I met code and the county inspector gave me a green light. The only thing he wanted was a larger grounding cable for the power. Easy fix.
Note - all the prices above pretty much include the rental of trenching equipment.
Bottom line is when you get a piece of property you like, consult with the county on what you really want to do. My Land Contract included an escape clause if the county said that I could not do what I planned to do with the land.
Others are cautioning about services in a remote desert setting and I wholeheartedly agree. You may get a piece of land above an aquafer but you may not be able to get a permit to drill into it - your "rights" to resources under the ;land should be spelled out in the deed. Septic should be easy but as OldGator says I got a quote of $15k for septic as well. As far as a solar array to power a liveabord property you are talking 10s of 1000s IMO.
I will say that as a young man I worked at a sailplane camp in the California desert that had no water. We would haul 5,000 gallons of water in a military trailer and pump it up to the water tower. With a pump you could probably forego the tower but under the tower was also the crew shower - I can tell you there was no shortage of hot water after we made a ho****er bladder - LOL.
We also had a latrine pit which may not be legal today. Another option might be a porta potty?