I currently have an iPhone 4 which I have now had for two years. One of my other family members used my upgrade in February so I do not have an upgrade until 9/13. I would like to get an iPhone 5 so I am wondering if I can upgrade early, and how much it will cost?
You can upgrade at any time you would like if you pay full retail. I believe iPhones start at $650.
When you say you can't upgrade until 9/13. Is this when your family member's line is eligible for a discounted upgrade? If so, chances are you would not be able to get a subsidized upgrade thru Verizon until then.
You may want to check a site like Swappa.com if you can't swing the full retail price.