I would have one partner create a separate page/contact form specifically for the advertiser – so only people who see that contact form are people who were referred to by the advertiser. The advertiser would use that page as their outbound link. I know you can track outbound clicks in Google Analytics events and Contact Form conversions (usually through most contact form plugins) but that is the best way I think. Never done it, but this is how I see most affiliate programs like that work.
Join a startup accelerator: Another great option is to apply to a startup accelerator like Y Combinator, 500 startups, or TechStars, where a group of investors will help coach you, connect you with potential partners, and provide startup cash in return for a small stake in your company. The competition is tough to get into these, so don’t rely on them as your only path forward.
If you're serious about making money online, start a blog. Blogging is one of the easiest and most sustainable income sources. As long as the blog is setup the right way, in the right niche, with the right content targeted at the right audience, and the offer is complementary to the content, you could make a tremendous amount of passive income from a blog.