One Water Heater in a Duplex

[Benjamin Andress]

Hello everyone, this should be a fairly simple question for those who have experienced something similar. But I am new to this :)

I recently purchased my first investment property. It is a duplex with 2 br in each unit. There are two boilers (one for each unit), but only one water heater. I am assuming this water heater runs on electricity/gas from the lower unit but I am unsure. We also only have one water meter for the house. 

I had a section 8 inspector come out and they took issue to it and I have since decided against section 8 anyways. 

How should I go about working this out with my tenant? At first I will be living in the upper unit so I was considering paying the water bill as well as maybe garbage while the lower unit will pay for the water heater - for both units (which will automatically be on their bill). 

When I move out, this situation would become a lot more interesting so I am looking for any advice anyone may have. Any input would be greatly appreciated. 

Thanks,