Bought mine on the Bay. they are fairly available there (look for a reputable seller and you should be ok) the 64gb N5 are on average under $400 for US carriers.
Make sure you ask questions though. I wouldn't want to buy a year old phone especially since the battery isn't user replaceable. I always ask how old their phone is
Buyer beware on Craigslist. Ask for the ESN or the IMEI number. If seller refuses you need to go on your merry little way.
And if u pursue with Craigslist seller ask to meet at the carrier store.. So if Verizon meet up at a Verizon store. You want to make sure the phone is clean... Meaning in good standing.
Sellers on Swappa Amazon and eBay are safer if getting used. Personally if this King used I would go the ebay route and get square trade for ins. I would hate to see anyone get ripped off.
Sometimes a deal really isn't.