I saw many peoples who claim that they have made thousands of dollars or earning $10-$100 daily from their adsense website, sell their adsense website for the price which they can earn in just few months from their adsense website as of what they claim they have earned or earning from website.
Whenever i find such website for sale, one question comes in my mind always that why they are selling their money making website? As of what i know such websites don't require maintains as they are autopilot.
I saw few peoples who do this work as a business. Just look at Complete Web Sites For Sale!
section of WF.