Does it cost money to use FaceTime on your iPhone?
buy them from itunes
Does it cost to do facetime with people on the iphone 4?
No you only need a WiFi connection which does cost money.
Does it cost money to get an apple id for your iPhone?
No, an Apple ID is completely free.
Can you use facetime on the iPhone 4 if whoever you're talking does not have an iPhone 4?
No you both have to have an iphone 4 :)
Does it cost an money to run an iPhone 4S?
Yes. With calls and the electricity for charging it text and Internet usage.