Shaker Heights, OH - Question on utilities for Multi-Family

[Chris Russell]

I just closed on my first multi-family located in Shaker Heights, OH. It is currently a two family house (first floor and second floor apartments). Each is separately metered for gas and electricity-which the tenants will pay. It has a finished 3rd floor that could easily be made into an efficiency apartment (I would literally only need to add a door to the shared stairwell to the 3rd floor). The 3rd floor already has a full bathroom and just needs a hot plate. I should be able to rent it for $400-500/month. Also, is should not impact the 2nd floor rent by more than about $50. 

Question: Currently, the 2nd and 3rd floors run off the same gas and electric meters. What options do I have in this scenario? Assuming I create the efficiency apartment, can the 2nd and 3rd floor tenants split these utilities like 60/40 or 50/50? Given the low rent for the 3rd apartment I don't want to pick up the cost of the gas and electricity for the 2nd and 3rd floors as it would largely negate the benefits of the added rent. 

I would appreciate any thoughts you may have. Especially if anyone has been in a similar situation. Thanks