Depends on the build date (month) - there's a pretty significant difference between early and late 2016 builds: Fit/finish was much more of an issue in early 2016 than later in the year. Then there's AP1 vs AP2 hardware (cutover in Oct 2016). Plus, keep in mind that white CA carpool stickers issued in 2016 will become invalid at the end of Jan 2019. Given you're in LA, provided the car is local to you, you might want to check when (if) the previous owner got their white carpool stickers.
I have an early 2016 X90D with roughly the same miles. My only "major" issues were failure of the active spoiler, fixed at around 5000 miles, and the acceleration shudder (discussed in several other threads here) which mine happened to develop at around 18000 miles. But it was easily fixed by the service center. Beyond that, the car has been great and I've only had to take it into service a few times for flat tires.
I will be posting my 2016 Model X 90D 6 seat, Pearl White, Tan leather, AP1, 20K miles for sale shortly in the mid-$80K range. I have June 2016 build, and as my avatar shows, I was all over the fit and finish issue before I got mine. Those early 2016 may have more challenges than later. I have no fit/finish issues that I care about on my care, and I am sure if you took calipers you could find issues. It does not effect the joy of ownership, and I am happy to say I have not had to take my car to shop since one month after delivery in July 2016. Wind noise comes and goes from passenger triangular front window, but I can't say I am aware of it as a problem to need fixing. Tesla told me they cannot drive to 85-90 mph to test the noise, so I guess its a minor issue. All else is great, plus free lifetime supercharging is great value-added sales proposition. Anyone PM me for more on my sale.
Our 2016 X P90D turns 2 years old next week! It’s been great in the fit and finish department, no issues in 2 years and 30K miles other than a failed door latch that happened about 5 weeks ago. It was pretty much time to service the car anyway, so got it into the SC for service and they replaced the two front door latches with the new models via their retrofit kit.
While there were more fit and finish issues with earlier builds, I wouldn’t have any issues buying a 2016 X with the caveat that I would want to see it in person and test drive it first, before finalizing the deal.