Graffi said:
1. What other sources can I find used Tesla's for sale.
I'm been working off and on to build a website dedicated to buying and selling used electric vehicles. While it's getting closer to an initial release, it won't help you today unfortunately. Used Teslas are sprinkled around the usual automotive sites (cars.com, AutoTrader, eBay, Craigslist) as well as on the Tesla Motors Club forum. One tricky aspect to shopping through the traditional sites is that you can't easily search on battery size and other EV-specific attributes.
My opinion is that the best way to buy a used Tesla is currently through Tesla Inc. However, many of their pre-owned vehicles are not listed on their website. My advice would be to contact a large sales center such as their Buena Park store. Tell them that you have a Model 3 reservation, but that you'd like to see if you can get into a pre-owned Model S sooner. I would not hesitate to get an older car with higher miles as long as you can verify that it comes with the standard pre-owned warranty. Some cars might be described as "as is", meaning that Tesla won't fix any minor, pre-existing cosmetic issues that might exist; this was the case with our used Model S.
Graffi said:
2. What features should we get: Must have, Should have, Would be nice to have, Don't need. Is any Model year preferred over another?
I understand that newer cars tend to have better fit and finish, and that some of the newer versions of parts may be more reliable. Our 2012 Model S has body panels with somewhat uneven gaps, which doesn't bother us but might be an issue for some. About a month after we bought our car, the panoramic roof exhibited a leak. Thankfully, Tesla replaced our V1.0 pano roof with the most recent revision of the pano roof, under the pre-owned warranty, instead of repairing it piecemeal.
If you go on road trips, definitely get a larger battery (85 kWh for an older car, at least 75 kWh for a newer car). Also, verify that your car has the "tech package" if buying an older Model S.
We really like our pano roof because it makes the car feel more open and provides additional headroom. The tinting is great, and we don't feel hot. Some folks with cataract issues may find the light from above to be unhelpful, though.
One of our requirements was the rear facing child seats, for a total seating capacity of seven. The ventilation doesn't reach back there so well, though, so we bought a portable 12V fan, a 12V extension cord, and a 12V "Y" adapter. Otherwise, those seats are a great addition.
AutoPilot "1.0" was available on cars from approximately late 2014 through late 2016. Many people love it. I suppose its potential value depends on the sort of driving you do. Personally, rather than putting money into an AP 1.0 car, my thinking was to hold out for something closer to full autonomy. The AP 2.0 cars are supposed to have the hardware necessary to eventually achieve this. I'm cautiously optimistic.
Graffi said:
3. Budget I should need for the various Model Year, mileage, and options included.
I'm not sure if anyone has a really good pricing model for used Teslas at this point, though some are trying. For an older Model S, I'd maybe shoot for close to $40K, which could require some patience.
Graffi said:
4. What trip planning tools does Tesla have that will not only get us to our destinations, but plan our Super-Charger station stops. Does it give up to date access and availability?
My family has found the built-in nav system to be quite useful in this regard. It predicts energy usage and shows it on a plot compared with your actual usage on the current trip. It shows nearby Superchargers, incorporates them into the route as needed, and shows current availability/congestion.
Graffi said:
5. Any other recommendations you think we would need when searching for our new EV.
If you buy from Tesla, be prepared to wait, as they don't generally prep their used vehicles for sale until orders come in. And be prepared to order a car sight unseen. Just make sure to inspect it for cosmetic issues prior to making the final payment. The warranty should cover any real, functional issues.