Gigs ni nini?
Good thinking, you basically want to be a marketer/salesperson. Negotiate with supplier for a cheaper deal than the end user and the difference between what you charge end user and what you pay the supplier will be your commission.
You may stand a better chance if you at least provide one of the services, e.g decoration, then as you offer your services you link the event host with the other facilities from your suppliers.
I expect it'll be tough at first but once you have established yourself it will pay, the job is competitive though. But nothing comes easy and you'll get smart as you move along.