There was a man who was struggling to make ends meet, so he decided to take up a job as a door-to-door salesman. He went around selling vacuum cleaners and was actually quite successful at it, but he soon realized that he was getting tired of all the rejection he faced on a daily basis.
One day, while walking through a residential neighborhood, he came across a house with a sign that read, "Beware of the Dog." Ignoring the warning, he rang the doorbell and was greeted by a very large, menacing-looking dog.
The man was terrified and started to back away slowly, but the dog just stood there, wagging its tail. Feeling a bit braver, the man reached out his hand to pet the dog, and to his surprise, it licked his hand and wagged its tail even more vigorously.
Relieved, the man said to the dog, "You're not so scary after all! Why is your owner warning people about you?"
The dog replied, "Oh, I'm not the dog they're warning you about. I'm the vacuum cleaner salesman."