Submeter cost too high worth to include gas in the monthly rent?

[Antonio Porta]

We really want this 3 unit property in a nice area. Heres the challenge: 

Presently 2 oil tanks there. One burner is gas, the other oil burner.  2 units are on 1 gas and 1 electric meter.  Cost for the  conversion from oil to gas ONLY is $7,000.   This would make it more efficient but still is only 1 meter. The contractor said that he does not sub meter for gas, as I would have to call others, which I do not have an issue doing, but said it may cost triple to have separate meters for Gas. I am looking into actual cost, I want to be able to make an offer with considering the cost to sub meter gas.

As a landlord I feel like I would have to include gas in the rent? 

Ive read on here that some landlords calculated the sq footage or price per person and split the utility between the units that way.  It would make it much more easy to just have them separated. The cash on cash return is much more unpredictable with gas being included, and this is concerning for me.

I am wondering how its worked out for other landlords who do any of the above I mentioned and if so, have you gotten any push back from current or even prospective tenants?  Or has it been difficult to rent when a tenants moves out? 

As far as electric goes,  I am looking at submetering electric, We have a  cousin that is an electrician so it should not be too costly. 

Any thoughts are appreciated. THANKS!