You'll find that car-trunk living is fun & affordable. You don't need a big car. You can do it in a Fiat. Firstly, remove as much stuff from the trunk as you can. Next, install a single bed in the trunk, night stand & portable toilet, kitchenette & small fire place. Also: You'll need a way to cool your trunk. You can use a window-box air conditioning unit or a swamp cooler. I usually just use my car's air conditioner, but you don't have to if you don't want to.