What is the bare minimum qualification required to be a recruitment consultant?

[Old Greg]

Agent: Good morning, I am calling you regarding an opening at one of our clients ********.
Me: Thanks for the call, but I am already being represented, and am in advanced stages of the process.
Agent: Oh, is it? Well never mind. Do you have any friends who might be interested in this role? You can earn 500 in referral bonus if they are selected for this role.
Me: <In my mind>So you are suggesting, I refer my friends as my competitors for this role?</In my mind> Why would I do that?
Agent: Well you can earn 500 tax free!
Me: Thanks, but I am sure, I can earn much more even after paying tax if I get this role.

</ slam the phone>

Why would you tell the agent that? A half decent agent will let slip to the client that they've got your CV to put forward and you're pretty insistent, but they've already secured you a contract elsewhere, so would esteemed client prefer they didn't put you forward?