your basis land vs building is generally the same as the donor's. in other words, you step in the donor's shoes but paying that $100K could mean that $500K retains its original basis land vs building (500/600 times her cost basis for building with the rest to land) and you use appraised values to split the $100K. you're responsible for recapture of depreciation she took if property sold. the question is how much. so it might be that the building portion of that $500k is depreciated using the remaining life at the time of the gift and you start depreciating the building portion of that $100K using 27.5 years. consult a pro also Turbotax may not be able to properly handle the depreciable portion of the property.
you did not mention fair value of the gift, if less then above does not apply
