You sure do.

What if someone is test driving one of your cars and totals a school bus full of kids?

What if someone steals one of your cars?

What if your building burns down?

Actually, the thing you don't really need is product liability as far as the car having a mechanical problem. You can sell the new owner a policy for that. Of course, you would want to be covered if they went one block from your place and a wheel fell off and they went through the front door of a c-store.

And you need to be covered incase someone ribs you, falls down on the pavement and breaks a leg, throws a brick through a plate glass window and all the other things any business needs insurance to cover.