While there are other sites such as Craigslist, AutoTrader, etc. where you can shop for used Teslas, they really aren’t created for electric cars, especially not Teslas. You can’t search/sort/filter based on Tesla-specific options, and they’re overrun with ads that often times don’t even differentiate between Model S sub-types. Even sites that claim to cater to electric vehicles or Teslas specificall don’t work well, are clunky, and don’t allow you to manage your own ads.
Facebook or other social media groups can be a decent place to look for a used Tesla, but it’s very hard to see more than the last day or so of posts, so many good deals slip through the cracks, and it’s really hard to find what you want as there’s really no filtering beyond price.
Buying from Tesla and getting a CPO car is probably the next best way to purchase a used Tesla Model S, after Find My Electric. Because, you’re getting the satisfaction that Tesla has checked the car over (you can have them do this for any car you’re considering buying though), and they often provide a 2 or 4-year extended warranty for used Model S vehicles (sorry, Model 3, no extended warranty for you). But, you’ll often pay a lot more than you will from a private seller, and there is NO negotiating with Tesla, so forget about that if you’re thinking you can talk them down to a lower price.