How much is it for an iphone 4s or an iphone 4?

So i'm planning on buying an iPhone 4 or 4s I'm not sure if their both the same thing but i'm just 12 so I don't know. I want to know how much it costs monthly, I also need some information from those of you who had had this iPhone 4/s. I don't have much money so don't tell me to get an iPhone 5c or whatever. Right now I have about 300 dollars in savings. (I work for money) I get paid 40 dollars a month so I think I probably have enough for iPhone 4. Please ANSWER.
p.s. I have T-Mobile.
Thank you!

Added (1). my poppy will get mad if I don't buy a phone in 3 days.

Sent a package with USPS without persons name or return address

So I bassicly ****** this one up I sold an iPhone and I shipped it priority 2 day small box the persons address was on it however I failed to put a name or my address incase it needs returned I only have 50$ insurance on it and shipping confirmation do you think it will be okay?

Buttons on my iHome (iH4P) aren't working?

When I plug in my iHome it is on full brightness and it says that it is 12:00 PM. I try to change the time but the buttons aren't responding. When I plug in my iPhone it says that it is charging and it recognizes that it is plugged into an iHome, but the iHome doesn't and will not play the music over the speakers. The low battery icon is flashing, but I tried plugging it in without the battery and the same thing happened. The battery is just the backup battery. Is my iHome broken, or do I just need a new battery?

Pregnancy test result positive?

I took a dollar store pregnancy test. The same I have used my last 2 pregnancys… The last 2 pregnancys came back positive right away. This time I saw a quick line of pink that then went away as the test kept reading, then the solid pink line then appeared. Well after the test strip dried, I could see the negative line AND the positive line, positive line you can clearly see where the strip is, but vet very little pink if any at all. I hear if it's truely negative you can't see the positive line at all. So is it negative or is it positive? My IPhone can pick up the positive line but like I said very very faint as if nothing were there but I CAN see where the positive strip is clearly just no or very little pink. I do plan to take another In the morning as this one was last night.

Why won't my iphone turn on?

I was on an app on my phone I locked it then I tried to turn it back on and it wouldn't happen. So when I got back home I charged it and still nothing happened. If I turn the silent switch on and off it still vibrates. But when someone tries to call me it won't vibrate or anything. Please tell me what's wrong or what I should do.

IPhone 5 - Sound not working?

I was listening to some music before and the sound randomly stopped, no explanation

The weird thing is, the alarm sounds works, I recorded a voice clip and it played back, but the music doesn't work and nor do the ringtones… The alarm sounds work and play normally

I can't fathom it out; before you suggest, I've done the power/middle button "reset" things

Any ideas?

Should I update to iOS 7 for iPhone?

I have an iPhone 4 and was wondering if I should update to iOS 7. I like the way my phone is now and it doesn't have any problems, so is there really any benefit to updating? And is it hard to get used to the change?

I bought iphone 5c off craiglist?

I recently bought iphone 5c it has icloud account that won't let me reset the phone. The owner said he bought that way, and he doesn't have the password, and he won't refund. I have all the text messages, and we were in gas station where there was a camera too. What to do? Should I call police? Please advise