Many people in my industry have attempted a min-site model to monetize their unused domain names. My impression, which is based on a large amount of admittedly second-hand information, is that this business model is seldom viable. Several years back, the story might have been different.
If you're going to try monetization with AdSense, only unique content will do. Google is notorious for suddenly canceling AdSense accounts that flag their system for any reason; and there is seldom any redress, even when such cancelations are unwarranted. So don't invest your time in this monetization strategy unless your content is unique and all your SEO and traffic 100% white-hat.
Most people seem to pursue a mixed monetization model. For one thing, those income streams add up. But I'd stress that it's important not to put all your eggs in any one basket. In particular, I distrust the Google basket. If your livelihood depends on upstream advertisers, then diversify.
Affiliate marketing definitely works, depending on the niche, the site, and the affiliate program. But no 2 cases are alike.
Lead generation can be very profitable as well, if you know how to do it.