You can try ebay or Craigslist in your area. If you decide on Craigslist have the seller meet you at your carrier corporate store. If they don't agree to that you know something isn't right.
There is always a risk buying used, as said above, meet at a corporate store and activate on the spot. Check out the phone to make sure it isn't a fake.
You can also buy from sites like cowboom, easy to return if any problems, they cost more than ebay and cl, but are safer.
You can also wait for a sale on a new one, the Verizon Note II was $50 on contract before, factory sim unlocked. Then pay the $350 etf For about $400 total.