I personally would not purchase a used cartridge. It is a very fragile piece of technology. There is no way to know how much it has been used, This is me… actually I don’t touch a cartridge… my dealer does. My rule of thumb is buy nothing used with moving parts. So, no CD players. Audio equipment with no moving parts can be a great deal.
That is me. The pull of a good deal has been offset by the disappointment of the failure of what I bought… when I was young.