The garage could be a negotiation point, too.
Hey, how much gravel would you need to pour a concrete pad for a driveway and garage?
I would just need to have them pour a pad for a garage and then build a carport, because I would need concrete footers to support the weight of walls, although I am pretty sure that a roof would be heavier.
When I went to look up geothermal the first site said they switched to heat pumps because of how efficient the new ones are.
Then I found this:
Is this data averaged for the entire country? Electricity, natural gas, and propane costs vary throughout the country and so do heating and cooling needs, but if a heat pump costs significantly less to use than an electric or propane furnace, I might want to calculate the ROI.