IPhone 5 Locked Networks. Buy Contract?

I know that an Iphone 5 locks itself to the network of the first sim used, but. If i took out a contract with vodafone for example, could i, in theory put an ee sim in it first? I want too keep my current EE contract as my personal phone and use my existing samsung with the new contract for business. Would this work?

Added (1). The iPhone 5 is different, and it locks to the first sim used.

I always thought if you got a phone from apple then it was unlocked to any network! But if you got the phone from a network provider? Then the phone was locked by them to there network?
If that is the case though it is pretty easy to get the phone unlocked ain't it? And in the long run this is probably the best option anyway as this way you can put whatever sim you like in the phone whenever you like.

CPW iPhones are UNLOCKED but will LOCK PERMANENTLY! To the first sim card.

iPhone from APPLE are unlocked if bought sim free.
The Samsung will need to be unlocked as it is Orange & you want it to be YODAfone

As long as you are happy for the IP5 to be on be on ORANGE

Try here: http://gsmunlocklabs.com/unlock-iphone/