You asked
Is the nikon d3500 worth buying used?
Yes, I think the D3500 is a sensible used buy. It's small, simple, and good on battery life, and it's Nikon's last entry DSLR, so it sits on the Nikon F mount with a huge range of lenses. Buying a body that's a generation or two old is one of the easiest ways to save money, as I explain in buying used. You can read more on the Nikon D3500 page.
Two things to check before you buy. The body has no stabilisation, so pair it with a stabilised lens such as the Nikon AF-P DX 18-55mm f/3.5-5.6G VR if you shoot at slow shutter speeds. And budget for a new genuine battery, because old ones lose capacity.
Written by Claude from this site's pages.