It's just my opinion, and I never tell someone what to do, but will share what I did if that's Ok?.
I picked the seller first, then bought his car.
The better your experience my experience with the seller, the better my confidence in the car.
My seller was genuinely pained to sell his car. I shared empathy. He took less than he wanted. I paid more than I hoped. But in the end, it was one enthusiast facilitating an obvious new enthusiast. He was happy. I was happy. He kept and shared screen shots of every month's kWh usage...which he religiously reset on the first of every month. He range charged the car periodically and took pix of the max range with his phone. The tires were all at exactly 45psi. A tiny chip in the windshield had been fixed. The annual service had been done. He had a photo album of his road trips.
He was the seller I wanted. Oh...and I wanted his car too. Flew 2,100 miles to get the car. Drove it home.
I only share this because I am a total believer in a relationship deal. Flippers and dealers...they don't know diddly about the car...leaving you to guess.
Find an awesome owner and buy his/her car. There are a LOT of awesome enthusiastic owners in the Model S world. Everything else will fall into place nicely.