Can I make an iPhone for another carrier work for T-Mobile?

I'm thinking of buying my brother and I iPhones, but I don't have AT&T, Verizon, or Sprint. I have T-Mobile. I know nothing about this, so my question might be a little vague, but what does it mean when you might not get 3g speeds? I know you're supposed to jailbreak for it to work. Also, where would I buy it from (should I buy from Best Buy or the actual carrier store)? I checked on the Apple website, and for the unlocked, it was $549.00. Would I have to buy one from one of the provided carriers, or buy the unlocked one?

Why is YouTube so slow on my iPhone 5? - 1

I can't watch a video because it pauses every 10 seconds. I've tried through the app and through Safari and I've tried with Wi-Fi on and off - nothing helps. This is ridiculous for such an expensive phone and I'm on YouTube all the time. Anyone know why this is or having the same problem?

Wholesale online shop based in Korea?

Does anyone know any wholesale site in korea? I mean the shop is based in Korea. The products that i'm looking for are apparels.footwears, hair accessories, wigs, hair irons, cosmetics, iphone cases and cute items. I'm in abusiness so average prices of products is not ok itsbetter if they are cheaper.

IPhone 5 texts sometimes are really slow?

So I just got my iPhone 5 and half the time when I text it can take up to 3 mins to send the text. But sometimes it's just fine and sends it instantly. It doesn't seem matter where I'm or if I'm connected to Wi-Fi or not. Any idea what is wrong? Btw I have Verizon if that matters.