This old lady walks out of the grocery store and goes to the bus stop.
An old guy is sitting in the parking lot in his car. He drives over and
says he'll give her a ride home.
On the way he looks her over and says "You're a pretty good looking old
broad. I'll pay you ten bucks for a piece of ass".
She says "What???!!!". But then thinks that the old age check isn't due
for 5 more days, so she agrees.
They are lying on the bed after its over having the usual smoke and he
says to her "Geez if I had known that you were a virgin I would have
offered you $20.00!" 
She looks back at him and says "If I had know you could get it up I would
have taken off my pantyhose!"