how much does this fuckstick want for the car? is $3500 his asking price?
if you do decide to buy it after doing a mechanical check-up i'd offer him $2000 and in the end pay no more than 2500.
show him the cash and if he says no then turn around and walk away.
no one but an assclown tries to sell a car with a check engine light on.
get the hell off my lawn.