Assuming the OP has fairly modern phones, I doubt he has much to worry about. Most new phones with electronic ringers use something like .2 REN or something. Cordless phones are often 0.0 REN, since all it has to do is trigger the circuitry in the handsets. They're all battery powered anyways. The number of phones has no effect on the talking circuit, unless you have a bunch all off hook at once like an ad-hoc conference call. Otherwise, to the best of my knowledge the only limit to the number of phones (branches) on a single line is the available ringing current. If I'm talking crap, please- someone correct me.