unlocking without new sim card

[Andis Jackson]

I am getting a 3G iphone for the holidays, and a friend of mine is going to buy my 2G iphone, but he is on t-mobile. The only thing is he wants me to unlock the phone before I sell it to him. I've jailbroken and restored dozens of times, but I've never unlocked one. Do I need the t-mobile sim card in the phone when I unlock it? Is there anything in the settings menu that would let me know the phone is unlocked prior to placing the new sim into the phone? Just basically want to know if I have to have his sim in order to do this.

Thanks in advance for the help.

[dejawoo]

Basically if an iphone is unlocked once u can use any gsm operetor's sim card with it.U can use it with orange,at&t,tim&whatever u want...