I've bought quite a few used computers over the years, both laptops and desktops. Found some real deals. I haven't looked for them specifically on the membership site I promote, but I'm sure you'll find some there. There are a number of companies that sell them, often trade-ins by large corporations who are upgrading theie systems.
You can read about the site by clicking here -
http://www.thewholesaleforums.co.uk/...-list-but.html
Or, you can click the top link in my signature below and go right to the sales page for the membership site. It's not pretty, but it tells the story well.