What can I do w/ a Jailbroken iPhone?

[gottafly]

I'm trying to understand the benefits of jailbreaking an iPhone. In particular, how will I benefit from jailbreaking as far as the monthly fees/data charges? I've got a 3G that I'm not using as I've recently upgraded to 3GS. I'm considering letting my son use the iPhone on my AT&T plan but don't want to have to enroll in the data plan. Can he use it as a phone/ipod w/ wifi, but no data (and no contractual commitment)?

Is it possible to use it as a prepaid once it's jailbroken? and how does iTunes and buying apps work w/ a jailbroken phone?

Any insight is greatly appreciated.

[jmann]

I'll answer what I can. You won't have to sign a contract if you already own the phone. AT&T will just set you up with a new number/line. You can do pay as you go if you want. Also app purchasing works the same as it does on a non-jailbroken phone.