I have no idea why you'd sign another 2 year contract with Sprint, just get the IPhone for Life Plan which is $50 a month, Unlimited Everything, and about $20-$23 extra to lease the 6 or 6 Plus.
Your bill will be significantly lowered to around $73 a month for Unlimited everything.
$20-$30 for the iPhone 6 and $25-$35 for the iPhone 6 Plus. So it would range from $70 to $85. This is on the 24 month lease. They now have a 12 month and 30 month lease for the iPhone 6 and 6 Plus. If he's on the Everything Data or Unlimited, My Way Plan, there is a loyalty credit of $15 for users without a spending limit on their account that would be applied as well for the duration of the lease if they stay with their current plan.