Here we go.
If you are at all into post apocalypticism, check out the March issue of Harper's magazine. William Vollman, author of numerous books has an article about camping out with homeless people in Sacramento, CA, his home town.
Just about anyone who is into post apocalypticism can probably find some homeless campout spots in their home town. These seem to be more popular in California where the weather is mild. It's raining right now and gets near freezing at night but at least, there's no snow on the ground. If you want to do some post-apocalyptic exploration, you can probably spend a night in some homeless camp and see whether you really like the idea of post apocalyptic living or not. Or you can just buy the Harpers issue and read about it. Or you can forget about the whole thing and watch the trailer about flesh eating zombies.