You asked
Is the nikon d850 worth buying used?
Yes, I think the D850 is a strong buy used. It was announced in 2017 with a 45.7-megapixel full-frame sensor, and it's still excellent for landscape work. Buying used is one of the best ways to get good gear for less, and a body a generation or two old often gives you most of what a new one would. The Nikon D850 page has the full specs and every lens that fits its Nikon F mount.
Two things to check. The body has no stabilisation, so pair it with a stabilised lens for slow shutter speeds. And budget for a new genuine battery, since old ones lose capacity (see buying used).
Written by Claude from this site's pages.