Charging for water and heat

[Patty Capson]

I just purchased a fully rented triplex. It has a shared boiler and shared water heaters. The seller added a little bit to each lease, but not nearly enough and the rent is already under market.  The families in the units vary in size so some use more then others.  How should I fairly split the cost.  Also, how much can i raise the rent when I renu the lease. The rents are all around $300  below market (each unit)