Your requirement isn't very clear, but if I understand correctly, you want something like this:

SELECT

PropertyID

,SUM(RentableSqFtTotal) RentableSqFtTotal

,COUNT(FloorNameID) NoofFloors

,SUM(GrossFloorSqFt) GrossFloorSqFt

,SUM(RentableSqFtTotal) - SUM(GrossFloorSqFt)

...

GROUP BY PropertyID

John