Do you buy used carts/needles? Is it risky?

No I do not buy used cartridges. The only person I would buy a used cartridge from is me. 

@audphile1 ,

If you pay by check, do you wait for it to clear before you give it to you??

Something I might try some day, as I've also got a 1200G with removeable headshells to make it easy to switch. Currently using a Hana Umami Red that I got new on a trade-in. I would suggest getting the best cart you can afford, as I've found that makes a much bigger difference for me than the TT itself. And of course your phono preamp plays a big part.... 

vinyl no s vinyl is both plural and singular. 

I did some years ago. No issues ever.

My first AT OC9 was a used cart which I bought from a reputable audio dealer in the late 90’s. It probably had less than 100 hours on it., it sounded great.

Still have it, it was superseded by an OC9ML, and a few years ago by an AT 33PTG/II .