Insurance salesman

One day an insurance salesman knocked on the door. Little Johnny answered the door and was asked if his mother was home. Little Johnny said, "No, she's at the whore house." The salesman asked if she was a prostitute, and Little Johnny replied, "No, she's a substitute. She only works Wednesdays and Fridays during the rush." The salesman replied, "Well, I'll be a son-of-a-bitch." Little Johnny said, "Heck, I'm a son-of-a-bitch too, but I don't go around knocking on doors telling folks."