Other than the rolling back of the odometer (which just ensures that they get a hefty discount off their vehicle), it's not a big deal.
It's not like they embalmed the bodies in the vehicle, nor were naked corpses lying directly on the floor.
Nor will the spirits of the deceased be lingering around to taunt the folks who bought the van
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Haggling for stuff is fun, too. If I were to buy a car, I'd walk in, give a low low price, and if they didn't like it, I'd wave bye bye! Usually they come runnin after ya
If they come back with a counter offer, lower your original price to get what you want:
You: "25,000"
Salesman: "How about 30,000 instead?"
You: "Okay, 24,500 or I'm walking."
Salesman "25,000 it is."
Salesmen rip you off only if you let them. If they have a car they're trying to get rid of, trust me, they'll do anything. If you don't play a pushover, you can pretty much get anything you want and walk away with a sweet ass deal.