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

I like variety to spice things up.  It is the only way I could afford top cartridges: Koetsu Corralstone D (maybe best musical cart), VDH Grand Cru, Aida Mammoth Gold (gold coils) with zero to extremely low hours). 
When purchasing, I highly scrutinize the seller looking for near to 100% positive feedback from at least 10 sales. Established dealers I’d usually trust to perform.

But since it seems you’re asking to save money on normal wear, interest in cartridge rotation seems minimal. So I’d simply try to purchase new at the lowest price or one with extremely low hours, then run the cartridge until noticeably worn. If stylus replacement cost is an issue, then I’d take a hard look at SoundSmith cartridges.  

If you can afford to buy a 1200G- you can afford $850+tax for a new one.

Used carts can be a great buy, especially higher price point models-$2.5K+ or so.

Naturally, one must do their due diligence in making sure who you're buying from.

That means more than just an email exchange.

My used cartridge purchases were always what was advertised.

Get the new Hana, AT OC9 or whatever. There are many great sounding options well under $1K.

I would highly recommend used cartridges. 
As mentioned know who you are purchasing from. 
i usually try to exchange numbers and talk direct. 
 

I purchased a Hana Red this week. 
it came as advertised. 
I paid 1/2 of the new cost. 
could not be happier. 
Good Luck 

I love buying used. I've bought new too, and that can be OK with discount - but I've never needed to file a warranty claim, and don't expect to. Buying used on USAM or Audiogon really isn't high risk, with a few simple guardrails. The guys selling $3K used cartridges generally aren't the same kind flipping a 1990s Corolla or PlayStation on Craigslist. Look for a straight cantilever and signs of corrosion. Sure a guy could lie about hours, but I suspect most of us are conservative on estimates and fall on the honest side.