Hello, i live in Brazil, in the state os Sao Paulo, and i want to buy the iPhone 4s, but first, i would like to know if it will be compatible with the 4g network that will arrive in Brazil in 2013. I don't want to buy the iPhone 5 because it's to expensiv

No the iphones 4s is only compatible with wifi and 3g networks. only the ipad 3 & 4 and Iphone 5 can be used with 4g networks. 🙂

Sorry to say this, but the iPhone 4S doesnt support 4G anywhere.

If you're particular about 4G, you have to go with an iPhone 5

I doubt anyone here will know the answer to this question. You need to ask the cellular provider where you live I think.

According to Apple (http://support.apple.com/kb/HT1937) there are four carriers officially supporting the iPhone in Brazil. I would suggest you check things with them - note from that Apple link I pasted that all technical support in Brazil is provided by the official iPhone carriers, not by Apple. So, all the more reason why you want to talk with the carriers, as they will be your sole source of technical support once you get the iPhone you want.