Preusedev.com is the best way to buy and sell a tesla.
This site started out as a project to solve a personal need. I was looking to purchase my first Tesla vehicle. There were already a few price aggregators but none of them seemed to work reliably. So I built my own to send me an alert when the ideal configuration became available for sale, then followed-up when the price was adjusted. This allowed me to find my perfect first Tesla, a black Model S.
After having built the first version of this site (previously called teslacpo.io) for my own purposes I figured that others could use it as well. So I made it a bit more generic then opened it up to anyone to use. Sending out over a million email alerts and helping numerous buyers find their first tesla. I never qualified for the free roadster or any of the really cool things Tesla used to give away in their referral program but I am still working through a few free supercharger miles!
The latest version of the site has been designed by my friend Josh Deane. It features more customizable alerts, the ability to save individual cars and private listings. I've used it to find my most recent Tesla, a model X and I am currently using it to look for a model Y.
I hope that others continue to find the site useful. I also love hearing about how others have used it to find their ideal tesla.
P.S. I do consulting work (techinical architecture, full stack develpment, interim CTO, application development, etc.) on various technology stacks. Reach out if you've got a challenging project...