Under the laws of most municipalities, each rental unit must have its own separate water and utility meter to avoid the problem that you are writing about where each tenant is required to pay under the terms of his or her lease water and utilities.The only exception is when the rent is a flat monthly rate where the landlord picks up the costs of the utilities. I suggest that you consult with your local permit and resource department about the requirements for separate meters for each of the rentals in your complex.