Is there a way to use an iPhone's internet (not wifi) without service?

Hi. I'm not sure about this, I have done a lot of researching, and I haven't found anything that is recent. Any forum threads are outdated and maybe this wasn't possible then.

Basically, I'd really love to buy an iPhone 4 or 4s without a contract. I am not financially able to pay for the fees of data for the iPhone and for the voice and messaging plan. I already have a phone, but I'd really like to own an iPhone.

I have a few questions:

1.) If I buy an iPhone 4 or 4s from ebay or craigslist and it's unactivated, I'm sure I won't be able to do anything but dial 911, and maybe just basic things. I'm sure I can't download any apps from the app store even on wifi, or those are things I've read, you have to unlock the phone first, right? Or am I wrong?
And if I'm right, what do you have to do to unlock it? Jailbreak it, and then what (if that's what you have to do)? I have tons of experience with the iPod touch and jailbreaking and using it, so jailbreaking isn't a problem, I'd just like to know what I'd have to do to use the iPhone without activating it on a wireless carrier.

2.) Once I get it unlocked/jailbroken, is there ANY way to use the 3G internet on the iPhone without having it connected with a wireless carrier? Like downloading an app or something from cydia to be able to unlock/use the 3G? I don't have a data enabled phone now, so I wouldn't be able to share my current phone's internet with the iPhone. I also don't have wifi, and it's very hard to find wifi and get to it. That's why I want to know if I can use the 3G or any way to get internet on the go without paying, or maybe if there was a small fee to do this, I would pay it. I just can't afford to pay the current data cost for the iPhone, or activate it with a wireless carrier at all. I'd like to use it for google voice and also to download apps from the app store and use the internet on the go, without being connected to wifi.

Maybe I am wrong about number 2. But is there any way to get internet on the go with the iPhone without having it activated on a wireless carrier? Any way at all? No matter how complicated, I would like to try.

Thank you for any help.

 

Thanks for all the answers, though some aren't very nice. And I have to try the Unicorn Tethering!!! (yeah...)

I do have a 3rd gen ipod touch and getting the Peel seems like THE option for me. Just a question, from what I understand, you have to use a sim card, otherwise, you don't get internet, right? Or am I wrong again? If you have to get a sim card to use the Peel (and get internet), then which carrier would be the cheapest with data included? I am aware of T-Mobile, and people say they are the cheapest, but I think there might be a less popular carrier with cheaper plans.

Basically I'm trying to spend the least money I can to have an iOS device and use data on the go, and the Peel seems like the best option. So I'm trying to figure out what the cheapest supported GSM wireless carrier would be that allows data, and possibly unlimited texting and maybe unlimited voice, but I'm fine with limits on voice. The data is what I want most.

 

Unfortunately, I don't know anyone who uses a GSM network. Just CDMA.

I'd really like to know the cheapest carrier.