Build a Website - wanting to pay someone for job based on commission from website

Hello, Am wanting to create a website for a fitness event coming to Brisbane in the next few months. The event involves all participants (up to 2000) signing up and paying via the website. The website is also a source of event information. The event will be held monthly so this site will have to be setup in a way that supports this kind of traffic/payments. Will need credit card integration. Probably through Stripe. I do not wish to pay for the job up-front. I am willing to pay the successful designer a 5-10% commission of all fees paid through the website. This is a MASSIVE opportunity for a long term relationship as this event will be here for a long time and will also open in other cities. Your job is to design mockup, design logo, develop website (including all payment integration). Needs to be responsive. I really want a website where all the info is on one page so a parralax website could be good. Though I don't mind if you have other ideas. Here are some example sites below.... [login to view URL] [login to view URL] [login to view URL] Examples of similar