Who pays what bills?

[Mike Lalor]

First time poster here.  I am looking to buy my first rental.  When it comes down to who is in charge of paying for what bills, do I the landlord have control over that?  for example i notice some rentals the renter is responsible for the water bill, in other rentals they are not.  Is this all determined when the lease is signed?  If i purchase a property with people in the middle of their lease would i have to wait to change these bills until the end of the lease?  

thank you so much in advance