sisters of st francis

a man is driving down a deserted road when he sees a sign saying:
sisters of st francis house of prostitution 10 miles.
thinking its a figment of his imagination he keeps driving.
soon he sees another sign saying:
sisters of st francis house of prostitution 5 miles.
he keeps driving then sees another sign saying:
sisters of st francis house of prostitution next right.
curios he pulls into the car park and sees a small sombre building named sisters of st francis.
he knocks on the door which is answered by a nun who asks
"what may we do for you my son?"
I saw your signs he answers and was interested in doing business
"very well " says the nun "please follow me"
she leads him down a long corridor then stops at a door"please knock" she says
he does so and another nun with a tin cup answers the door
"please place 50 in the cup" the nun instructs
"then go through the door at the end of the hall"
the man gets 50 out of his wallet ,places it in the cup,
then walks eagerly down the hall and walks through the door pulling it shut.
as the door locks behind him he finds himself back in the car park,
next to his car facing another small sign saying:
go in peace. you have just been screwed by the sisters of st francis