The bulk of geothermal (GSHP) systems are the pipes that are buried far underground. If you currently use oil, you may be able to get rid of or at least substantially downsize the size of your oil tank. Many people worry about the longevity and upkeep costs of this type of system because the bulk of the cost goes into burying the pipe underground. Recently however many companies have been offering 40-75 year warranties on the parts of the system that is buried.
If you already have a forced air oil or gas-fed furnace system it may be easy for you to convert to what is called a “dual system”. In this case you would choose which heating and cooling system would.