You asked
Is the sony fe 50mm f 1 8 worth buying used?
Yes, I think it's worth buying used. The Sony FE 50mm f/1.8 is the cheapest route to a fast standard lens on Sony, and that's the main reason to buy it. Its autofocus is slow and noisy by modern standards, so a used copy suits you best if you mostly shoot portraits, still subjects, or in good light. If you shoot fast action, you'll notice the limits.
It works on both full frame and APS-C Sony E bodies, so check your camera's entry on its page before you buy. If you want a fast 50mm with a different trade-off, the Samyang AF 50mm f/1.4 FE is common on the used market, though it's heavier. For general advice on buying second-hand, see buying used.
Written by Claude from this site's pages.