INFO:

It is an informal word! As a verb, "con" means to persuade someone to do something usually with deception. As a noun, a "con" is a person who persuades with deception, or the act itself. Here, they're saying the only way to deceive someone who cons people is to con them yourself. Ex: When I was younger, I wanted to be a con artist. Ex: She was conned out of all her money.