Your best option is to upgrade using Verizon EDGE. It's their financing program, lots of benefits and it ends up being the cheapest way to upgrade.
Take the full retail price, divide it by 24, that would be your monthly installment but the first one is a few cents more because the retail price doesn't divide evenly by 24. Sales tax is due upon placing the order. With EDGE there's no upgrade fee ($40 per line if you upgrade by way of a 2-year contract.) With EDGE, you get a $25 per line discount if you have a More Everything plan of 6GB or higher, $15 per line if its less than 6GB. For an iPhone 6 the monthly installment is around $32 (for the 16GB version), less the $25, that's $7 per month you pay with your phone bill. The sum of payments is about $168. With a 2-year contract you pay $400 per phone, plus tax, plus $40 per line, putting you all in for about $500-$520 depending on your local sales tax. You do have to hand in your old smartphone as part of the EDGE offer but you can get around that - Verizon waives the trade-in requirement if the phone on the account is a basic phone. And with EDGE Verizon is more forgiving on early upgrades, letting you pay off the remaining balance early so that you can upgrade whenever a new phone that you want comes on the market.
