On a completely different facet of the topic, I have occasionally thought about the feasibility of living in a minivan. An engine with a small displacement could idle for a surprisingly long time on not much gas, which would keep the alternator spinning to generate electricity and provide heat or air conditioning. Remove the middle seats, put a TV tray in front of the back seat for your laptop and voila!
You could hang out in the Walmart parking lot for bathroom access (you'd be buying a lot at Walmart anyway because you're already right there, so nothing unethical about using their restroom) and Pilot or Love's truck stop has showers.
If you want to get innovative you could fill the front right side with car batteries (connected in parallel, not in sequence) drill a hole through the front dash and charge them off the car electrical system, then disconnect them when you turn the car off. Then you have power that doesn't depend on the car idling all the time, with no risk of running down the battery that starts the car.
The downsides would be annoying... No pets, no cooking, no fridge and you'd have to cross the parking lot to pee no matter what the weather is. Sure you could get a hot plate and a micro fridge, but that would take up precious space in a small area. There would be little space for stocking reserves of food and water. Your main reserve would have to be money, and that continually depreciates with inflation.
Also most vehicles don't last as long as most houses, and if your car broke down it would be a major inconvenience instead of a minor annoyance. It's almost impossible to find a mechanic who is both good and available to fix your car at a moment's notice.
