I have lived in this area for years and not sure that's true.FYI, renters usually pay for these services separately in an apartment complex.

I assume that even the water is metered separately?  

If the tenants paid through the Company B portal, the full rent would've been sent to Company B and what is left between the previous owner and Company A would be separate and irrelevant.

It is a tri level house that sets up very well for house hacking with three separate common areas and a large backyard.

Unless it's been on two separate meters since it was r6, in which case there's a grandfather allowance.

The city quarterly bill has broken down the expenses into separate water and sewer costs, and the sewer is hovering around 400% more than the water.

Those two stay separate so you have receipts for your CPA and income/expenses is not "muddied."

The property is currently listed on the MLS as two separate properties when they are actually both sides of a duplex. 

I would advise opening a separate bank account for the real estate related activities if you are treating the real estate as a rental.If it is 100% a personal residence, no need.

This has the benefit of letting me immediately start renting out both sides of the property (after cosmetic repairs).Or I could purchase the duplex as a House Hack opportunity using an FHA loan with ~3.5%, down, receive a lower overall interest rate, and use the remaining funds to purchase an additional rental property, separate from the Duplex to increase the overall rental property portfolio.