We've done some integration with SEMrush that gives you some pretty good info about a site that is up for sale. Included info: Back link profile compiled by SEMrush spider Total links Follow links Nofollow links Unique linking domains Unique linking IPs Estimated organic traffic Number of keywords the domain ranks for Amount of traffic The dollar value of organic traffic they are receiving Show the top 10 organic keywords the site ranks for (including position, AdWords cost for those keywords, etc.) Anyway, you can see a sample of the data for digitalpoint.com (on the old test thread I did when I first made the auction system): https://marketplace.digitalpoint.com/digitalpoint-com.11230/domain