When I was on the top floor I notice one room only had a space heater for heat, which I thought did not qualify as a heat source. 

As with any older house, there were some things that needed work, like it had no A/C and only radiant heat (built in 1978), so dealing with that was tough while HVAC was installed, but learning to be a landlord was a great, but tough lesson.

@Ivan SarabiaIf your lease states they are responsible for paying their own utilities then I would do the following:Call the utilities company and remove my name from them.Give the date the utilities will be shut off to your tenant.If they choose to live without electricity and gas for heat I guess that would be their choice.Look up what your state law is about water service.Good Luck!

As a result, when Seller’s Pepco account was eventually closed today, the property ended up having its pipes burst due to no heat.

We have a really expensive heating and plumbing company who does the same.

**All of this Info has been gathered before approaching the Owner**Property Info:-Built in 1940's -12 Unit Building 6-(2Br/1Ba) 6-(1Br/1Ba)-Tax Value $1,300,000-Annual Taxes $16,000-Current Rents are ($850 for 2/1) *couldn't find info on (1/1) but it is well below market Value-1920's Renovated Building in the area Rents for ($1,245 2/1) and ($1,045 1/1)-No Property Manager (owner managed)-Owner Pays Water and Utilities-All surrounding Apts. pay for Water/Sewer Only-(A Class Area) with Mixed Use Buildings and Student Living-Walking Distance to University-2 Units currently Not RentedRehab/Needs -(from what I can see)-New HVAC, has Radiator Heating and Window Units-Living Room Floor (Sinking in) on Top Floor Unit -Cracks in Interior Walls/Exterior Brick-New Roof (I'm assuming) Large leak in Top Floor Unit-New Fire Escape Staircases -Updated Electrical-Updated Plumbing (I'm assuming) built in 1940's-Interior UpdatingI know its a lot of Work, but It's in a great area, and there is a ton of room for Value Add.

Baseboard heating in the summer time not so much.

What are the loads in the house: electric baseboard heat; heat pumps; AC units; laundry; other motor loads.I am failing to see why you would need a 400 amp service without a proper load calculation.There is no code restricting the number of sub panels, they only have to have the correct install and protection.If I were in your shoes, I would connect with a licensed and insured electrician and ask for electrical audit. 

We'd be passing through all utility costs to our tenants, so heating/cooling efficiency in that standpoint isn't a concern. 

If you're any more than 0% through the useful life of any of the major systems (heating, roof, etc) you may need to adjust that number accordingly.Same for Vacancy and Repairs.