I got a refurbed iphone 4s and it was perfect in every way. You can still buy refurbed thru a carrier then when you go thru the plan there's certain options you choose if you just want a phone. I almost bought a refurbed 6 last month but couldn't justify spending $700. (I need a 64 since there's no 32 anymore and 16 is not big enough for me).
You can also try Facebook (yes facebook). There are thousands of buy/sell groups. just start joining them and searching for "iphone 6" I bought my son's iphone 4s from someone on fb. Couldn't be happier and at least I knew the person's name and what he was about, not like craigslist where you could be dealing w/ an ax murderer. lol.