I think they may be referring to the rumor(?) that the VZW iPhone 5 is already unlocked for GSM use.
To the OP, if you are referring solely to unlocked sim then if they aren't already unlocked you will need to be a VZW customer (you can pay full retail and be on a month to month contract). If you are referring to a fully unlocked device...to the best of my knowledge, other than the rumor that the VZW iPhone 5 is gsm unlocked and can work on AT&T in the US (not on 4G LTE though) there is no officially unlocked version of the iPhone 5 that is sold in the US. You can keep checking Apple's website to see if they will start selling them like they did the 4s...but in that instance you could not get an unlocked CDMA device so the 4s would only work in the US on AT&T and T-Mobile.
I thought I read an article Verizon the one good thing gift it gave you by buying 1 was an unlocked Verizon iPhone 5 tgat you can use it anywhere.I think it was huffington post written after release .
Mdram even when you bought the 4s full retail it wasent unlocked. I thought by what I read it could have been a mistake that it was unlocked but it was.
Here is an article to prove that Verizon iPhone 5 is unlocked from the start
This is what I was referring to as "rumor" as there seems to still be questions on the validity of the claim. As far as the iPhone 4s...yes, the CDMA version could only be unlocked for international use but Apple did/does sell the 4s unlocked BUT it will not work on CDMA networks...so if you bought it you could (and many have) use it on T-Mobile rather than on AT&T if in the US...or any other GSM network.