How long does it take for a phone carrier to unlock a phone?

I bought an iphone from someone on the Internet and need to have it unlocked in order to use it. The phone is locked with sprint. I talked with sprint and the person that sold me the phone. The person then talked with sprint and said the phone will be unlocked in 2-3 days?

It depends.

Too long

And you trust this person?
It is more likely than not that the phone will not be unlocked!

Why did you pay money for a phone that you can't even use?

It generally depends on the carrier. However, the STANDARD TIMEFRAME for unlock request is typically 2 business days.

If everything is in order & conditions are ideal, the request could be processed in as little as 15 minutes. Then it's just following the steps to unlock the phone. In the case of iPhones, you will need to connect it to a computer that's online with iTunes & do a back-up & restore. As part of the restore to factory settings (prior to restoring your backed up data), iTunes will get in touch with Apple… Which in turn, gets in touched with your carrier about the unlock status of the phone. Once Apple gets the OK from the carrier, it'll send the unlock "flag" to the iPhone.

It is recommended to wait roughly 24 hours from when you receive the "Approval" message from the carrier to complete this as there can be a delay between Apple & your carrier. If the phone is still not unlocked, you (or the original owner) should contact the carrier for assistance.

2-3 days.

Why was it not unlocked before buying? I would always make sure that is the case first.

So sprint told the guy you bought it from that the phone will be unlocked in 2-3 days. Hmm, I doubt it will ever be unlocked and the phone is probably stolen. What did sprint tell you?