By far the best way to buy a website is to search for a keyword you are interested in on Google. Now ignore the first few pages of results, and look through positions 30-100 for sites that are clearly under-monetized or look abandoned.
Good sites are selling for 24-36+ months profit - grab yourself an under performing site from the search results and you can be in profit within a few months.
If a site is already page 1 when you buy it, its hard to get really good returns on it, assuming it was monetized reasonably well to begin with. Its extremely hard to get a better ROI than buying a page 4 google result site that was monetized by Adsense, then ranking it page 1 and monetizing it properly 8)