Louis Rossmann has been fixing Mac’s at the component level for years. He knows MacBooks inside at out, he knows why the fail, and he knows which ones are more durable and which are designed poorly. Be sure to check out his YouTube page HERE.
Used MacBooks are getting harder to find online, since Amazon just signed an agreement with Apple to only allow new Apple products and no refurbished machines. Fortunately you can still pick up a used MacBook online at Mac Of All Trades.