You asked
Is the 7artisans 18mm f 5 6 worth buying used?
Here is what the site says about that.
From 7Artisans 18mm f/5.6: 7Artisans 18mm f/5.6: A prime lens by 7Artisans for Full frame cameras, 18mm f/5.6. Specs - Maker: 7Artisans - Focal length: 18mm (prime) - Maximum aperture: f/5.6 - Made for: Full frame sensors - Mounts: Sony E, Nikon Z, L-Mount - Stabilised: no - Autofocus: no, manual focus What it frames like - On full frame (Sony E, Nikon Z, L-Mount): as marked, 18mm. - On APS-C (Sony E, Nikon Z, L-Mount): like ...
From Buying used: Buying used: Cameras and lenses are built to last, and many photographers upgrade often. That makes the used market one of the best ways to afford good gear. A body that's one or two generations old is often most of the camera for a fraction of the price.
Quoted from this site's pages.