There are many freelance options for graphic designers who are looking to make money online. Designing layouts and graphics for promotional material, corporate reports, magazines or book covers, are all tasks that businesses are looking for online freelancers to complete. Due to its flexible nature, graphic design possibilities can range from one-off projects, to ongoing work with regular clients.
If you are building a site that has the potential for information that will never age and remain useful for your audience, you have the opportunity to create what is known as evergreen content. It's important to carry out extensive keyword research before planning any evergreen content for a site like this, as your site could hugely benefit from the proper usage of keywords within such content.
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.