You asked
Is the sigma 60 600mm f 4 5 6 3 dg dn os sports worth buying used?
Yes, I think it's a good candidate for buying used. Long lenses hold their value well, and a used copy is the easiest way into serious reach without paying full new price. Buying used explains why this works.
The Sigma 60-600mm f/4.5-6.3 DG DN OS Sports is made for full frame and is stabilised and autofocusing. It reaches 600mm, but it gets darker as you zoom in, so expect to raise your ISO or shutter speed at the long end. On Sony E, the Sony a7 III and Sony a9 II are both on its fit list. For what to shoot with it, see wildlife and sport.
Check that the listing says DN, since the older DG OS HSM version is a different lens. If the price is well under new, I'd buy it.
Written by Claude from this site's pages.