Using affiliate ads is one of the common ways to monetize a site. Most common affiliate ad networks do not even have any kind of requirements and you can get approved for zero traffic. For instance, you get auto approval form Amazon Associate. Clickbank, Shareasale, Linkshare, Commission Junction, etc. can be easily used for low traffic websites. Some affiliate ad network have high traffic requirement but the payment is also very good. What kind of affiliate ads do you use? Do you have a conversion?