That's a conflict of interest and grounds for termination. If you worked for a company, and had a side business to teach suppliers how to sell to that company, you'd be fired.
At my Big Corp (tm) we just let someone go because he offered a service to coach vendors on 1) How to get on our supplier list and 2) our internal criteria for vendor selection. He also charged for the service and as IT Ops head had a great deal of say over how this worked internally.