Combined utilities in duplex

[Jill Herges]

Looking for some advice on a duplex I am evaluating.  It is a great deal on paper, but the utilities are not separated out.   It is an up and down duplex in a 1915 house so I suspect separating them out would be costly at best and not possible at worst (without a complete gut of the interior). The current owner bills the tenants for the actual utility bills.  If I do that, do I just split it 50/50?  One unit is larger so by default it will use more heat and electricity.  My real concern is what recourse I have if they don't pay? If they don't pay rent I can evict, but could I put a clause in the lease regarding utility nonpayment? The bills will be in my name so I will pay them regardless. Just wondering what others have done with combined utilities?