I wish I did what it is that you want to do when I was your age. Unfortunately for me, I didn't want to leave the warm, comfortable bosom of my motherland, New Jersey, at that age. Since then I've traveled and seen a lot of the nation, and one dream I have is to still do something as you are looking to do.
I have considered buying a "shack" or building on of my own on inexpensive land that I would purchase and making it a home. So, I have been looking.
First of all, make sure you look critically at the Tennessee Smoky Mountains area; it is a big destination for wealthier people to go to live "off the grid". I've noticed a lot of those people are not truly living off the grid, although some are. Also, it's very politically charged in that they are mostly libertarians who are looking to "gulch" there ("gulching" is a move as far off the grid as possible with other libertarians/anarchists so as to avoid the government as much as possible). Personally, I would not want to live around such people. But more importantly - I've noticed that land and homes up there are not "cheap"; they're cheap for the older couple who is selling their $500,000-$1,000,000 homes in some reguular suburb and can afford $100K for an acre of bare land or $250-300K for an old farmhouse. No bargains, in my opinion.
For what you want, I suggest looking at parts of Washington State and Oregon, or parts of the Desert from New Mexico to Southern California. Arizona in particular has some very cheap land. I've noticed a lot of cheap land off the I-10 between Phoenix and Tucson. It might be wise to buy that land and put a trailer on it; in 10 years it will probably jump in value, as Phoenix and Tucson are growing towards each other. Also, northern Arizona around Flagstaff, and out to Kingman and Bullhead City (towards Vegas) is a lot of cheap land.
The only thing, of course, is to make sure you secure WATER. Water isn't as unavailable as people think it is in the desert, as long as you secure some rights when you buy. But other than that, it's cheap, you don't have to worry about paying for heat (although you may want to pay for air conditioning, but I've heard that swamp coolers do a great job). It IS indeed a dry heat, and although people tease about it, the fact is that dry heat is not nearly as bad as a humid heat.
New Mexico would be great too, because the land there is cheap also. You may be able to find some inexpensive old homes out in the desert. Desertsun gave some good tips in his posts in this thread, i'd investigate those.
If you don't mind snow/cold, one last option, which I was surprised to find so close to my part of the nation - Upstate NY. Mostly in the Finger Lakes region and north of it and west of it (but not too close to Buffalo). VERY cheap land, often with cabins already built on it. It does get cold and snowy, and spring is muddy and still cold, but summers are BEAUTIFUL there and autumns are spectacular. Summers will be nice and warm but not too hot, and not too humid (but humid, still); Autumns will be dry and cool with brilliant colors.
I wish you the best, I love your plan, I think you will really enjoy life. I realize what you mean about wanting to live simply - not necessarily off the grid, and probably preferably not off the grid, but remote enough to be inexpensive and where you can do your own thing.
I think Nevada/AZ would be good because you're close to Vegas which has a comic book "scene" somewhat, and So Cal would be near L.A. and San Diego. Washington/Oregon would be near Seattle and Portland. But NY State would put you near NY City (somewhat) as well as Buffalo, Pitt, and Cleveland.
Best of luck, let us know what you narrow it down to!