people who visited the site but did not opt in > you can use negative audiences for your ads with facebook ads, you just take visitors to the site and substract the people that visited the thank you page. For people who did not purchase, you simply can't with affiliate marketing unless the vendor adds a conversion pixel of yours on their thank you page.
If you want to clear some space out in your house and have a big stack of books you’ve been holding onto for too long, you can make money selling your books and textbooks online. Stores like Half Priced Books and others will give you cents on the dollar for each of your current books while you can check what your book is worth by simply entering the ISBN number on Book Scouter.
Research individual companies in your desired niche: If possible, it’s always better to become an affiliate directly with a company (if they have an internal affiliate program), as no one else will be dipping into your commission rate. This is the preferred route for most of the prominent affiliate marketers, including Pat Flynn. Unfortunately, it’s also the most work, as you’ll have to do the research yourself to see who offers programs (they’re usually listed in the website footer).