Buying an iPhone 5 from USA to use in Australia?

I'm wanting to buy an iPhone 5 when it's released later this month from USA because it's cheaper there.
My question is if buying it from the USA would it work here in Australia?

I tried to work this out with the iPhone 4S. I think it would work in Australia, but when you buy it from USA, it is locked to a 2 year contract so you'll have to get it unlocked somehow. You can buy it outright/unlocked but it costs a little bit more.
So it ended up being cheaper for me to get it in Australia. Would be pretty much the same for the iPhone 5 I think.

I'm interested in this phone because this iPhone 5 its cheep there