Unlock/Jailbreak iPhone 4/4s

Dear All,

I need a piece of information.

One of my friends has bought two pieces of iPhone 4 and three iPhone 4s, all having different iOS versions and baseband versions.

There are numerous sites available who are offering softwares and even online solutions (by giving IMEI), but I am not sure which one to go for :spinme as few (or many) of them are reported as fraud.

Please suggest if anyone has a trusted site in a reasonable amount (30 USD or less).

I might had tried doing it by reading different articles but I do not want to try it as I am scared of getting it bricked, and moreover it is not my iPhone.

Thanks in advance.

Regards,
Vikas