Here is a step by step for what it sounds like you want to know.
Set the vehicle up as an inventory item. (If you need help with selecting accounts or a good example of the setup, PM me and I can give you exact screenshots and possible a video walkthrough of the whole setup)
I would also recommend using class tracking and creating a class for your vehicle so you can more easily track the expenses associated with it. Set that class in the inventory items setup so it uses the class on any transaction for the vehicle.
When you purchase the vehicle, enter an Expense that shows you paid a certain amount for the vehicle from the auto auction or whoever sold you the vehicle. Make sure you also select the class for the vehicle in the expense transaction for purchasing the vehicle. This will increase your inventory by 1 for that vehicle and increase your inventory asset account.
As you incur expenses for repairs, cleaning, etc... select whatever expense accounts you have setup for the repairs and cleaning and other services you use to prep the vehicle for sale. With each expense, assign the vehicle class to the expense.
When you get ready to sell the vehicle, use an invoice or a sales receipt and select the vehicle inventory item as the item you're selling. Enter the price you're selling it for a long with any other items you may be selling with it. (Extended warranty, etc.) . Make sure the vehicle class is set for all the lines of the sale as well. This will decrease your inventory asset account, increase your cost of goods sold as well as your income account for the sale.
Once you save the sale transaction you can run a report like a Profit and Loss by Class that will show the expenses you incurred as well as the money you made on the sale.
I've attached a sample of the end report below.
Here is the info for this example that you see.
Purchased a Ford F150 from auction for $2500
Put in total of $1210 in cleaning and repairs and prep work to get it ready for sale
Sold it for $22500 plus an extended warranty for $500
Total income for this sale is 23,000
Report shows cost of goods sold as the original purchase of 2500
Gross Profit is 20,500
Expenses for this vehicle total 1210
Net Profit on this vehicle is 19,290