"Good Catholic Story" joke

A man is driving down a deserted stretch of highway when he notices
a sign out of the corner of his eye... It reads:
SISTERS OF ST. FRANCIS
HOUSE OF PROSTITUTION
10 MILES
He thinks it was a figment of his imagination and drives on without
a second thought... Soon he sees another sign, which says:
SISTERS OF ST. FRANCIS
HOUSE OF PROSTITUTION
5 MILES
Suddenly, he begins to realize that these signs are for
real... Then he drives past a third sign saying:
SISTERS OF ST. FRANCIS
HOUSE OF PROSTITUTION
NEXT RIGHT
His curiosity gets the best of him and he pulls into the
drive... On the far side of the parking lot is a stone building with a
small sign next to the door reading:
SISTERS OF ST. FRANCIS
He climbs the steps and rings the bell. The door is answered by a nun in a long black habit who asks, "What may we do for you, my son?"
He answers, "I saw your signs along the highway, and was interested in
possibly doing business."
"Very well, my son. Please follow me." He is led through many winding passages and is soon quite disoriented. The nun stops at a closed door and tells the man, "Please knock on this door."
He does as he is told and another nun in a long habit, holding a
tin cup answers the door. This nun instructs, "Please place $100 in the
cup, then go through the large wooden door at the end of this way."
He gets $100 out of his wallet and places it in the second nuns cup. He trots eagerly down the hall and slips through the door, pulling it shut behind him. As the door locks behind him, he finds himself
back in the parking lot, facing another small sign:
GO IN PEACE.
YOU HAVE JUST BEEN SCREWED
BY THE SISTERS OF ST. FRANCIS.
SERVES YOU RIGHT,
YOU SINNER.