I have thought about that, especially buying some vacant land for cheap around the El Paso area which is a frequent place where one needs to find a place to sleep. It wouldn't take that much money to have a bulldozer level the entire site, add an entrance/exit, paint some rough parking lines, then put an "iron ranger" in place with envelopes.
Well, until insurance, zoning, and taxes came into the picture. Then, there is the security aspect. I'm guessing a security guard is $20 an hour, so there will need to be at least 24 people paying $10 a night, every night, to make up for that cost.
The more I research campgrounds, the more I am amazed they make any money at all, especially with all the regulations, codes, and other items needed, for such a relatively low density.