Get an unlocked GSM phone with replacement plan ...
If you're going to buy any refurb ...
1. Get a replacement plan
2. Get an unlocked GSM phone (and you pick your GSM provider)
There are many, inexpensive replacement plans for 2 years, especially on refurbished phones that cost less anyway. Make sure they give you a credit (less plan cost) if you have to return your phone, and that way you can likely get a "better phone for the same price" when it does go.
And in this day'n age, get an unlocked GSM phone so you can switch providers when you want. Fuck free phones and contracts, get your own phone and get your own plan without a contract (or a short one). With GSM providers, you can switch easily with the change of a SIM chip.
For those of us that travel outside of the US, GSM is not merely a must, but an unlocked GSM phone is a must. US GSM providers love to screw you on international use. With an unlocked GSM phone, you can get a pre-paid GSM card for pennies per minute.
I've been all over the Americas with an unlocked GSM phone, and I've never paid more than $0.10/minute, if not only $0.02-0.07/minute (after initial card cost), with various, local carriers on a pre-paid card.