You asked
Is the zeiss biogon t 25mm f 2 8 zm worth buying used?
I think it's a good candidate for buying used. Lenses last a long time, and the used market is one of the best ways to afford good glass, as I explain in buying used. This Zeiss is a manual-focus 25mm f/2.8 for full frame with no autofocus or stabilisation, so there's less that can go wrong in an older copy.
Check it carefully before you pay. Look at the focus ring, check the glass for haze or fungus, and make sure the aperture works smoothly. It's a Leica M mount lens, so pick a body from the list on its catalogue page. If you buy a used body too, budget for a new battery, as covered in batteries.
Written by Claude from this site's pages.