If i get an iPhone 4S do I have to buy a plan, or network carrier when I get the phone or can I do that later?

Yes, you have to get a plan in order to get the phone, which is why it would cost $200. It's a discount price in return for signing up for a 3-year plan, meaning you're stuck with that phone for 3 years. However, you can most likely upgrade for a fee, depending on the mobile carrier you choose (Verizon, AT&T, etc.)

Same with my Samsung Galaxy S2X. I bought it for $50 and signed up for a 3-year plan with Telus. The full price of the phone is $600. I can call Telus at any time if I wish to upgrade my phone but continue with the 3 year term (which is probably what I will do when I have some money saved up so I can get the Galaxy S3).

When I upgrade, I will need to pay off the rest of my hardware discount ($15 per month for however many months I have left on my 3 year plan, which would be 30 meaning I would have to pay Telus $450 plus the price of the S3 on a 3 year term (I think it's somewhere around $200 or $250. I would then have to pay a total of $650 - $700 if I choose to upgrade to an S3 right now, but that means I can do whatever I want with my S2X (in my case, I'd sell it for around $250 or $300 plus all the accessories and a new SIM card).

As pricey as it sounds, you're essentially getting the iPhone on a discounted price and in return, you sign up for the 3 year plan. You can upgrade at any time, or you can wait for a year or two before upgrading so the remaining monthly balance on the phone isn't too much (it will go down by $15 per month). Or you can go through the entire 3 year term and then upgrade to a new plan with a new phone.

This would vary based on the mobile carrier and their policies on how buying a phone on a plan works. Hope this helps!

If you were wanting to use it as an iPod you would have to pay the off contract fee which I think is 650.00 for the 16gb model. If you buy the iPhone on contract you would need a data plan, and a talk and texting plan. If your family is already with at&t you could tack it on for about 45 dollars a month, sharing minutes with your families plan. If it is just you getting the iPhone and your family isn't with at&t you are going to be paying in the upwards 90-100 dollar range a month. When you get the iPhone for 200 dollars it means your committed to pay the month fee for 2 years, so give it a long think over. Hope my answer helped!

It is a mobilephone so of course it will want a service. Sure you could buy it on the Apple retailer (not iPhone store) but they'll ask which of the three carriers you could possibly need it for.