I have an iPhone 4 on a plan with my parents, and I'm (finally) due for an upgrade this week. We're not in the best spot for money and my mom is worried that upgrading will increase the monthly fee (we have the More Everything plan). I have no idea how it works and how upgrading to either the iPhone 6 or waiting for the 6s/7 (haven't decided if I'm going to wait for it) will affect the bill and I don't want her to have to pay more per month. Thankfully I have some money of my own now and can buy the phone outright by myself, but am not sure whether I would be better off upgrading through Verizon or going through another website like Craigslist. Supposedly the upgrade would offset the cost but I've heard that even with that, I might be better off still going with a 3rd party.
So, should I upgrade with Verizon or seek out a better deal elsewhere? If the former, what are the payment options and will they increase the monthly bill? And as an aside, any idea on how the cost of the 6s/7 when released will compare to the current costs of the 6?