I tried buying from Tesla there aren't any Model X SUV's available used.My two cents here, having just purchased a used 2018 X in April, take with a grain of salt.
First, get the X, if you’re at all conflicted, you’ll appreciate the size down the road. 30 seconds sitting in a Y at the Tesla shop was all it took to convince me that the hassle of a used X was worth it for the extra width and capability (it also tows a useful amount).
Second, buy direct from Tesla. They can ship it to you from anywhere in the country, you get a little extra warrantee, and you know up front if FSD was included. I asked multiple people from Tesla this, and they confirmed it. My X arrived with “FSD” as it currently stands, so just enhanced AP, summon, etc, and the service center has actually called me nagging me to get the HW3 upgrade.
All in all, buying a used Tesla was only slightly more difficult than ordering and leasing a brand new one, which is to say, really really easy compared with the typical car dealer BS. Caveat to that, you’re buying sight unseen, there are “standards” but there is some small risk involved with that. Two months in and I’m totally happy with my purchase and my new old X (it’s practically a classic now, for a Tesla).
but my first service appointment is Monday, so that may change.