You asked
Is the sigma 24 70mm f 2 8 dg dn ii art worth buying used?
Probably yes, if the price is right. Prices move, so compare current used listings with new before you commit. The buying used guide makes the case: lenses last, and buying second-hand is one of the best ways to afford good gear.
The II is a 24-70mm f/2.8 zoom with autofocus. It fits Sony E and L-Mount, and on APS-C bodies it frames like 36-105mm. It isn't stabilised, so you'll rely on fast shutter speeds or a stabilised body.
Check that the listing says "DG DN II Art" and not the first version, which also turns up used. Before paying, look over the lens for scratches and test the zoom and focus.
Written by Claude from this site's pages.