How long does it take to unblock an iphone 5?

I bought a blocked iphone and I told the original owner who said he will get it unblocked soon. He says he has done it but i'm still not recieving signal even after re inserting my sim? How long does it take to unblock it. And by unblock i mean blacklist he said it was rightfully his and he can call the carrier and sort it out but how long will it take

Well, if you're asking him after the fact, it might sometime around never. Typically a person has to show up in person, prove ownership of the phone and the account. Blacklisted means it is listed as lost, stolen, or unpaid bill. Unless he ponies up the back balance or you're sure he's the real owner, this might not turn out as you'd expect.
Settings > General > About. Look for the IMEI--the serial number.
Plug it into this to see if it's legit:
http://swappa.com/esn
Hope it's more than an expensive MP3 player paperweight for you.
Best luck.