It depends on how the bill is calculated. If each unit is metered separately, you are not responsible for other unpaid bills. But if the meter is combined, then unfortunately it might be the case. Just to give you one example I encountered several years ago, I rent one room in a 3 bedroom house, one of the room mates has financial difficulties and was late for rent, utilities for over a year. We ended up paying the utilities for him, otherwise the utilities will be stopped for the entire house.