Not sure if people are aware, but when you purchase an old house even one that has no depreciable value left in the building, all the internals eg curtains, carpet etc are all reset to zero age again so these will be depreciable.
This occurs everytime the house is sold and a new owner comes along. So yes even in the case of a 100 year old house, the new owner/investor gets to do depreciation report and depreciate carpets, curtains etc despite condition of these.