Can I buy any iPhone and have it unlocked for T-mobile?

I'm planning on buying the Iphone 4 or 4s and I was wondering if I can buy an AT&T or Verizon Iphone for cheaper and have it unlocked?
Most iPhone's that are unlocked go for an average of $170-250. Verizon or At&t iPhone's go for $100-140.

So what do you think?

What company are you investing in?

Do you believe that apple is good to invest in right now? Last time I checked a single share of apple is going for $95! I can imagine what the price will be when apple starts getting orders for the new iphone 6.

How to make iphone full screen on TV?

I bought a apple hdmi adapter so I could watch videos/ view pictures from my
Phone on my tv

I plugged it in but isn't full screen? Is there a way to make it full screen?

Cracked iPhone 4 screen won't work?

So i dropped my iphone 4 (not 4s. It's pretty old. Maybe 5 years?) a few hours ago at youth group. I tried turning it on and it lit up so i was relieved. Then I was looking at the crack. It's cracked really bad on the top left corner and goes down to the middle of the screen. After looking at it, i tried to text my mom and tell her what happened. The screen lit up and i tried sliding it to do my pass code, and it wouldn't do anything. I kept trying to slide it over, open the camera, or those little settings tabs on the top and bottom. Nothing would work. After trying for a little the screen would move, and eventually got to the keypad with a lot of struggling. I can't type my pass code in. The numbers won't work. And i went to go try and backup all my stuff, but it won't back it up because i need to type my pass code in. What do i do?!

Added (1). I also tried to turn it off, but i can't slide to power off. So i held the home button and the click on the top and it shut off. (i did this 3 times) i tried sliding and it wouldn't work. I also tried charging it, taking the case off, everything

Help is there a way to delete texts from my iphone from my computer?

My mom wants to read my texts so she took my phone. My phone is locked but i think she'll find the password soon enough. Is there a way for me to delete my texts from my computer? I can't get my iphone back because she has it. Please can someone help me? Can i also delete apps? I don't want her looking through instagram and such.

What's the best double din audio receiver?

I have a budget of about $200-$250. It has to be double din. Must have either USB iphone connection or AUX connection. Bluetooth is not needed. And if possible touch screen or at least without the stupid colorful lights all over it.

Can you use an AT&T iphone 5 with staighttalk?

I have been using an android phone that I bought from the straighttalk company for a while, but recently was given an AT&T iphone 5. I read that there's a card you can buy for the bring your own phone program, however, I do not want to have to change my number. Also, if you have done this, please let me know if you have had any issues!

IPhones having trouble texting?

Until recently, my friend and I have always been able to iMessage normally. But a few days ago, he started not to receive my iMessages. There was only one text he didn't get so we just kind of ignored it. But yesterday and today, he hasn't received any of my iMessages and is unable to send/deliver iMessages to me. We don't know how to fix it. We've tried turning our phones on and off but the problem persists. Does anyone have any ideas as to what's going on and how to fix it?