One day an insurance salesman knocked on a door.  Little Johnny answered the door.  The insurance man asked if his mother was home.

“Naw.  She’s at the whore house.”

The salesman asked, “She a prostitute?”

“Naw.  She’s a substitute.  She only works Wednesdays and Fridays during the rush.”

The salesman shook his head and said, “Well, I’ll be a son of a bitch.”

Little Johnny said, “Yeah, well, I’m one, too, but I don’t go around knocking on doors telling folks.”