The concept of "possum living", originally coined (as far as I know) by Dolly Freed in her 1978 book of the same name, is different from the concept of survivalism or preparedness. It is better defined as self sufficiency, another popular term. So what is the difference?
Survivalism and prepping are about preparing for some event or combination of events that will prompt the prepper or survivalist to make a rapid transition from normal life before the crash to a wholly different life after the crash. The reasons for the expected crash are varied, but most survivalists refer to it as either TEOTWAWKI (The End Of The World As We Know It), which I prefer, or TSHTF (The Stuff Hits The Fan, for the polite version), which just about everybody else prefers.
While possum living types may be survivalists as well, most of our preps are in our very lifestyle. For us, the S has already HTF. But to paraphrase the song, we feel fine. That is because we like living this way.
It takes a certain type of personality. Consider this hypothetical day:
You wake up, start a fire in the woodstove, go out and feed the animals. Probably pigs, goats and chickens, perhaps some Muscovy ducks and guinea fowl, because these types of animals thrive on small tracts of rough land, the type of land you can buy cheap. Be sure to take your shotgun, because you might surprise a deer, rabbit or raccoon feasting in your garden. That's free meat, and whatever you don't eat of it, your pigs will be happy to polish off. On the way out, check the water level in the cistern. Gather the eggs the chickens have laid, and go back inside to a now-warm kitchen to prepare a breakfast of mostly stuff you raised yourself. That's "eating local" at its best.
Of course if you're married, your spouse is sharing the chores, and if you have kids, so are they. The work is good for them, and learning how to do all this stuff, and the patience it requires, is part of their homeschooling.
After breakfast, you go out and start your pickup truck so it can be warming up. New F150? Nope, more like a 1976 Chevy LUV that you bought with a blown motor for $100, then dropped in an old Mercedes diesel engine you got for $300. While the engine is warming, you plug in the cable that takes the output from its alternator and adds a bit of charge to your battery bank. Then you load the tools and supplies you will need for the day, make sure any of the kids that will be accompanying you are ready, unplug the cable, switch the truck's engine over from the cheap homebrew biodiesel it has been warming up on to the even cheaper WVO (waste vegetable oil), and head out.
Turn on your pre-paid cell phone (that is not associated with your social security number, if you even have one) and check for any messages from folks seeking your handyman services. Swing by the grocery store that you have an arrangement with to pick up their throwaway produce, which you feed to your pigs. Then visit your regular restaurant stops, where you get their used cooking oil for fueling your truck, tractor and generator. As you drive from one place to another, scan the sides of the road for scrap metal, useful stuff other people are throwing away, and pallets and other scrap wood that you can burn in your woodstove.
Stop at the park and eat the lunch that you brought from home, then let the kids play in the park while you get on the Internet by tethering your cellphone to your cheap laptop (running Linux, of course, since it is free and better than Windows) and upload an article you wrote last night, then check Craigslist and Freecycle for stuff you may be able to use, and of course check ebay to see how bidding is coming along on those circuit breakers you picked up off the side of the road.
After lunch, you go to the scrapyard and sell whatever metal scrap you have, then head back home if there are no handyman jobs to attend to.
Back home, you weed in the garden and pick any veggies you plan to eat tonight and tomorrow, as well as some to sell to the produce stand operator. Any bugs you find, as well as veggies they have already gotten to, go to the chickens. (Yes, I know it was winter this morning, but it's summer now.)
Now it's time to do any repair or maintenance chores that need to be done around the homestead. There's always plenty to do. Perhaps you picked up an old dryer from the side of the road, or from a Freecycle ad. Rather than just taking it to the scrapyard like most scrappers would do, you could strip it. Put the usable hardware in coffee cans to store for the next time you need a nut, bolt or screw. Take the motor out to use for some future project or to sell on ebay. You can even use those nice, flat pieces of sheetmetal as barn siding or roofing, or as a shelf. Only after you remove everything usable do you scrap the rest of the hulk.
Once the daily chores are done, go to your small pond or the nearby creek or river to catch some fish for supper. Just before cooking supper though, start the diesel generator for its nightly run. If it's summertime, you will want to crank up the air conditioners. Run the electric water heater so everyone can have a hot shower, and the dishes can be washed (although you could also heat the dishwater on the stove). If you have a well, run the pump to top off the cistern. All this time, of course, you are also charging the battery bank. By managing your loads, you are using the full capacity of your diesel genset, whether it be a homebrew Lister setup or a surplus Detroit Diesel railroad genset. If it is wintertime, you can use the waste heat it generates to heat the home; in summer, it can preheat your hot water. This is a possum living generator; let the suburban survivalists have their expensive Honda backup generators and five gallons of treated gasoline to power it when the public utilities go down. You can fire up that Indian Lister clone in early June and run it 24/7 until the end of September if you need to for running an air conditioner; that WVO fuel is free and Listers were designed for continuous duty. The Honda would use at least ten to fifteen dollars per day in gasoline to do the same thing, and would only last a couple seasons of such use, whereas the Lister will last a lifetime. Same with a Detroit; they were designed to run continuously for decades, and have proven themselves capable of doing so.
A lot of people would call this homesteading, and it is; but the word has also come to encompass the hobby farmer who lives in an expensive, modern home on five acres of prime real estate while raising alpacas and miniature horses and working fulltime to pay for it all. The possum living homesteader may have bought his five acres for what annual property taxes costs the upscale homesteader. But he doesn't have to prepare for what might happen, because he is already living the same life he would be living, with perhaps a few modifications, after TSHTF.