Help me I’m an idiot.

Each car has to be its own inventory type item. Inventory type items have three accounts:
income - your sales income account
expense - COGS
asset - inventory asset

then you use that item on the sales document, when you do that several things happen
inventory goes down
the cost posts to COGS
the sales price posts to income
and you deposit the funds

Buying a car is inventory, it is not an expense. An expense might be replacing a battery to make the sale.

I can see no benefit to using a class for a car dealer, stop using them.

Thank you go much for your response.   The reason I was using classes is so that vehicle maintenance, body work, and repairs done before we actually sale the vehicle gets charged back to the right vehicle.    This is so we can see profit and loss by each vehicle.   Do you think that there is an easier way to see profit and loss by each vehicle?   

I think I would use Projects vs. Classes...but think either should work.

Purchase Car:

DR Inventory (Project A)

CR Bank/Cash

Maintenance/Repair:

DR Maint/Repair (in COGS) - Project A

CR Bank/Cash

Sell Car to Customer:

DR Bank/Cash

CR Revenue - Project A

Rustler recommends using Items, not sure what the advantage is, maybe automates this part of entry.

DR COGS - Project A

CR Inventory (Project A)

However, by doing above, the best you will be able to see is Gross Profit by car.  In order to see actual net profit you would need to be allocating Indirect cost (like Office rent, phones, salaries, etc.) to each car.