"I Don't Want to Give You My Payoff!"

Don't fight customers who won't give you a payoff on their trade, or who won't let you fill out a credit app on their behalf. You're job is to sell a car, not to fill out credit apps and get payoffs. Tell the customer politely that it's fine if they want to withhold that information, but that you need to at least get a commitment from them stating that as long as figures are agreeable, they will drive the vehicle home today.