Tenants paying shared utilities

[Joe Lutterbie]

Hi all!  This is my first BP post!.  I just purchased my first multifamily home with 4 units.  The units share water and gas so currently I am paying it.  I was wondering different ways that I could charge the tenants to make up for that pretty big expense.  I have read about surcharging the residents a certain amount (maybe $25-50/month)  Do I just include that in my loan amount or can that just be listed in the lease as a separate expense for the tenants?  For example I would like to still advertise my rents to be lets say $600/month but also have that $25 surcharge in the lease for their utilities.  Does anyone have any advise on the best way to do this or have other ways to have tenants contribute to shared utilities?  THanks!