You asked
Is the sigma 30mm f 1 4 dc dn contemporary worth buying used?
Yes, I think it's a good candidate for buying used. I call the Sigma 30mm f/1.4 DC DN Contemporary cheap, sharp and fast, which is why it's a classic first prime for APS-C. Lenses last a long time, and a used copy is one of the easiest ways to get that speed and sharpness for less.
I can't tell you what a used copy costs, so compare listings yourself. Check that the lens works properly and that the mount matches your body. It's made for APS-C, and it fits a wide range of mounts, including Sony E, Fujifilm X, Micro Four Thirds, L-Mount, Canon RF and Nikon Z.
If you're still choosing your first camera, buying used explains how to stretch your budget further.
Written by Claude from this site's pages.