Perhaps instead of selling a website, you thought of buying an already established online property with proven track record in terms of traffic and revenue. Obviously, as a buyer you would probably use either Digital Point or SitePoint.
The important question here is how to maximize your chances of investing in a good property which would indeed ensure you some return.
In the perfect world you could simply ask for live access to traffic and monetization statistics. But that's rarely a case. Sellers usually provide just some proof in the form of screenshots from analytics software or AdSense interface, etc. That's all nice, but you still should make every effort to perform proper due diligence before spending any money on your next website.
