It has separate gas, electric, two hot water heaters, etc. 

Is there a way that sellers should validate this information?

I think your points are all valid and you're definitely more savvy than me lol.

We have the highest Gas Tax of the 50 States.

In light of the fact that the leases are a scam I would not feel guilty but would still try to prove the leases are not valid first. 

This is a valid example of an industry that was eventually exposed as being vulnerable to fraud, and once it was exposed, people were like..."

Instant water heaters take up less space and come in electric or gas versions.

If it's because the neighbors are making valid complaints, maybe do something. 

We know that a dual fuel system would be more optimal, but the cost of running a gas line and venting is likely higher than adding another circuit for the heat strip.Furthermore, we are looking for recommendations for an HVAC installer in Chicago.

Of course, the virtual numbers that the tool spits out have to be validated "the old fashioned way" by confirming the assumptions the tool is making (comps for daily rental, occupancy, vacancy rate, seasonality, etc.)