HOW MUCH DOES A NEW IPHONE COST PER MONTH?

Hi. I’ve been formulation on shopping an iPhone and not long ago my old phone pennyless so I would similar to to get it earlier rsther than than later. However, I do not know what the monthly price would be. I am now on a family devise with total content messaging. Does any one know how most it would price per month to dump my old Razr and collect up a brand new iPhone? Or a beneficial couple would be good too. Thanks!