What is your objective?
Selling such an expensive car on your own is nearly impossible.
Auctions are dealer only usually.
If you pay $12k for a car, drive it for 6 months and then take it back to the auction, you will probably lose $2500-3500 after auction fees.
If you can get in an auction & buy, I would do that. Buy a repo for the best buy. But KEEP it longer than 6 months.
If you want to resell the car at a profit, you need to stick to cars under $3000, That way, in 6 months you may be able to sell it for what you paid.
If you just want to buy & sell cars, don't keep them 6 months unless you cant find a buyer.
Probably want to stock with cars from $1500-3000 and then try to sell for a $700-1000 profit right away.
I was a curbstone car dealer for a dozen years and did just that. Now, the area I used to operate is sort of a war zone. But it was good for me for a dozen years.