There was a college student trying to earn some pocket money by
going from house to house offering to do odd jobs. He explained this to
a man who answered one door.
"How much will you charge to paint my porch?" asked the man.
"Forty dollars."
"Fine" said the man, and gave the student the paint and brushes.
Three hours later the paint-splattered lad knocked on the door again.
"All done!", he says, and collects his money. "By the way," the student says,
"That's not a Porsche, it's a Ferrari."