Sites like Zyoin and WiseStep connect employers with prospective employees, many of whom are already employed and not actively job-hunting via networking. The main benefit is knowing who these qualified candidates are. Rewards for referring a candidate who gets hired range from $50 to potentially several thousand dollars. If you know a stream of job-seekers, this is a great way to break into the recruiting business without the need for overhead costs.
Drive for Uber or Lyft: If you're in a locale where you can find Uber or Lyft (or even one of the many competitors around the world such as China's Didi), you could easily make a respectable income. The hours are flexible and you can work as you see fit, making it perfect even if you currently have full-time employment but are looking to make some money on the side.
If you have pop-ups and optins on every page, I would have to think that it would be a lot harder to convince someone to link to it. Especially since the pages where you have your optins (and probably receive the most traffic) are probably the same pages that you have your best content on as well that you'd be hoping to pitch in your outreach campaign.