How much would an iphone be a month at sprint?

I'm looking for new phones and I really want an iphone! I found one that is only 49.99.So every month what would it cost? My Mom and Step-Dad and I all have a normal phone, no smart phone with internet or anything… Normal phones… So what would it cost if I have a smartphone and they both have normal phones. Anyone know?

1 smartphone and 2 regular phones with unlimited data & texting, 1500 minuites is $149
for 3000 minuites is $189
unlimited everything is $279

you also have a "premium data fee" of $10 for any iPhone

there are also state/local taxes which varies by location.