As part of Obama's stimulus package there was written into a tax credit for Geo Thermal heat pumps. (View attachment)
30% of cost to install including labor and ductwork. If you have a large apartment complex the potential for tax credit is virtually unlimited. This could be a great way to increase the value of your property and keep you utility bills at a minimum. Great potential for cash flow properties.
Even single family residences it would boost the value of the house. If you need to replace the furnace anyway this could be a great way to increase the value of the home, and make more money.