Are "unlocked" or used cell phones a good idea? Where would be a good place to buy one?

last time i checked unlocked phones were illegal, however used phones are usually fine

I use unlocked phones, and I like them! I can use my phone on any GSM carrier, which is nice. I figured out how to unlock my iphone myself, so now I don't have to pay more money to buy an unlocked one.

I worked for AT&T for just about 10 years and I will tell you the same thing we use to tell callers when the called in and had an unlocked phone that they could not receive picture messages. An unlocked phone can not promise that you will be able to send or receive picture messages or be able to connect to the internet. You may be able to send text messages but not a promise. I know even if you get the subcity unlock code it will not always help. I worked for tech support for AT&T I do hope this helps. Weather it be AT&T or any other company as a new customer it is possible you can get a FREE phone with new service and don't be afraid of Refrib. phones as they are as good and also come with a warrenty :)

If you own the phone, it is perfectly legal to unlock it.
What is illegal is to try and unlock a phone you've found.

look at pawn shops and craigslist.
i know nothing about unlocked phones.

I would never buy a used cell phone but that's just me