You asked
Is the panasonic lumix s 20mm f 2 5 worth buying used?
Yes, I'd buy it used. This is a small, light wide prime made to pair with the Panasonic Lumix S9, so a used copy is an easy way to get a wide, compact kit on a budget. Good lenses hold their value well, so don't expect a huge discount, but a used copy still costs less than new. Check the lens for dust, haze, and a smooth focus ring.
It also fits other full frame L-Mount bodies, such as the Lumix S5 II and the Lumix S1R II. If you buy a used body alongside it, budget for a new genuine battery, because old ones lose capacity. See buying used for more, including what holds its value and batteries.
Written by Claude from this site's pages.