The inspector couldn't determine the age of the two gas furnaces.My question as a buyer is knowing that these appliances are in theory going to "burn out" within a few years (maybe months), how should I approach the situation? 

In my area, National Grid is the utility provider, and if you have gas service, they must be provided access to the inside of the unit to test all appliances if gas service has been shut off.  

gas here is $4.99, milk$6.99, a gal of water is $5.99 in the store. 

Sure, there are options out there like wholesaling that don't take much money but mailers aren't free, gas when driving for dollars isn't free, etc.  

Heat/Fuel=gas/forced air.

Does you know approx what it would cost to add a separate meter for electricity, water and gas since now it is part of the main house and I want to rent out the in-law unit separately.

I spend more on gas in a week than he spent on his mortgage.

The owner (myself) is currently paying the gas because the units are not sub-metered.  

Each lots are 1/4 an acre with stubbed out city water/sewer, gas, and high speed cable internet with sidewalks and paved street.

We also found that the gas lines all had to be replaced because if there was an arch, it would poke a hole in the gas line.So after this, we said we're walking away.