Can you do that finance thing that T Mobile does at the Apple Store or you have to go through T Mobile?
Only through a T-Mobile store, their website or by calling Customer Care.
Buying at an Apple store would require paying full price, but the phone will be factory unlocked.
i remember buying my 3gs and my 5 from an apple store for at
T-Mobile is different because now they don't do subsidies and upgrades on phones. You can still "upgrade", but all you're doing is getting a new phone--you won't get a discount on it.
If you check out Apple.com, you can see where it lists Verizon, AT&T and Sprint together, but T-Mobile has its own separate area with the full price showing.
BTW, the pricing for T-Mobile will be $528 for the 5C and $648.84 for the 5S. If you qualify, you can get the 5C for $0 down and pay $22/month for 24 months, or you can get the 5S for $99 down and pay $22.91/month for 24 months.