A man is riding down the highway one day when he sees a sign that reads "Sister Mary's House of Prostitution, 10 miles". He disregards it and continues driving.
A few minutes later, he sees a sign that says "Sister Mary's House of Prostitution, 5 miles". This one grabs his attention, and he begins to wonder what the sign is all about.
5 miles later, he sees a large sign that reads "Sister Mary's House of Prostitution, next right". The man takes the right, and drives up a long driveway that leads to a large wooden building. The sign out front reads "Sister Mary's House of Prostitution, enter here".
The man enters the door, and at the desk inside, there sits a young, beautiful nun. She looks up from her Bible, bats her eyes at him, and says "Can I help you, sir?"
The man grins largely and replies "I am here for your....shall we say....services?"
The young woman smiles and says "Follow me". He follows her to a hallway, where he is introduced to another hot young nun standing beside a door. She licks her lips at him, and says "Please put $20 in this jar, then step through the door. Close the door behind yourself, undress, and proceed through the door on the other side of the room, then close that one behind you." The man gives her $20, and rushes through the door. He tears off his clothes, and runs to the next door. He jerks it open, hops through, and slams it behind himself. As he hears the door lock, he turns around to realize he is outside the back of the building, naked as a jaybird.
He sees a sign in front of him that reads "You have just been screwed by Sister Mary's House of Prostitution. Serves you right, heathen!!!"
Cheesy, but it got a laugh out of me the first time I heard it.