There is no simple answer to your questions. Heating cost are dependent upon many variables.... including the cost per BTU, delivery charge for your utility and eve the particular home's insulation, the energy rating of its heating unit, etc. As you can see, there are many factors that can affect cost. In Chicago, if you want to know the average cost of a particular property you simply need to ask Peoples Gas for a disclosure. the form for the request can be obtained online.
Here's a link to People's Gas rates: https://docs.google.com/a/imovechicago.com/viewer?url=http:/
Hope this gives you a start on your project. Good luck!
Rusty A. Payton, Broker
1225 W Morse
Chicago, Illinois 60626