A smallish car can work surprisingly well if you are by yourself and creative in your sleeping/storage situations.
I spent 2 months living in a Peugeot 306. What made it doable was the fact that the rear seats could be completely taken out and the passenger seat could be slid all the way up to the dash. That left enough room for a camping cot on one side with a 40L water jug filling the footwell and holding up the head of the bed.
Then it was big totes keeping things organized on the other side along with a geared 26" unicycle all the regular camping gear (tent, chair, table, cooking stuff, etc), a couple weeks of food, extra fuel, water, etc.
The little car got pretty decent fuel economy and got stuck places FWD cars were really not meant to go.
I would have liked something larger but my budget was about 10% of yours and it worked surprisingly well. I only really used the tent when I was planning on staying somewhere more than two days. Small vehicles work but they need enough usable space. If I couldn't remove the back seat the tent would have gotten a whole lot more use.
The major downside of using the small car other than lack of room was the fact that it was not intended to continually travel rough roads with that much load and I blew out the shocks somewhere in the first 6000km of outback touring. If you have the money make sure you upgrade the suspension to handle the loads you are going to be carrying.
Now in the pipe dream section I am looking to buy an old diesel Land Cruiser and replacing the roof with a flip-top like a rooftop-tent. it won't be as fuel efficient but won't get stuck as easily driving up a dried up riverbed and have tons more room.
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