I won't do previously owned and used cartridges. I do have friends who swear by it though and they have always had good luck. Back in the day I bought and sold maybe 5 TT's and each either came or left with a cartridge. When receiving a used TT and cartridge, I'd test the table with a worn LP. If it sounded good to me, I would replace the stylus or consider a retip.
Cartridge new or used ?
How do I know if a cartridge is new or used and number of hours played ? 1- If it is bought from an individual or 2- Could it be that a HiFi store sells used or a "Demo" without anyone knowing it? 3- Is a cartridge that remains on the shelf of the store for 3 or 4 years, retains its same performance or its internal parts, can harden and lose their flexibility of reading? 4- Is it easy with a magnifying glass to see the wear of a cartridge, if so what would be the best magnification to use?