Just finance it for 8 years. :tup:
Here, this might help you figure out what you can afford:
http://www.finaid.org/calculators/loanpayments.phtml
Don’t forget about tax.
I wouldn’t finance a used car for more than 4 years. 4 years at $280/month at 7.5% interest makes a principle of $11,600. Take out taxes and you can afford a $10,600 dollar car. Add your trade in and it goes up to $13,100. Not a $20,000 dollar car unless you finance it longer.