What is your experience making the tenants pay utilities on a single meter

[Bobby Narinov]

I'm evaluating an apartment complex (two buildings) where the owner pays water, gas and sewers. During the inspection I noticed that some toilets have constantly running water and the wall heaters were still heating despite 110 degrees outside and the evaporative cooling running full blast. The tenant pays for electricity but obviously not high enough otherwise they would have turned down the heaters.

So my question is, is it possible to convert the leases after purchasing the property (probably one by one as they expire) and make the tenants pay utilities. Since the buildings are pretty old, I suspect re-piping would be extremely expensive and the hot water is still provided by a single water heater per building. 

What are the pitfalls of doing so? The rents are market but most of the other places are paying for their own heating and in some for their own water but the tenants are people on disability and food stamps.

How did you organize the payment? split evenly between the apartments, per person or some other way. How do you deal with the cases where the bill comes 2-3 months later?