Usually for buildings one uses 4% straight line i
Usually for buildings one uses 4% straight line i.e. for a building worth 100,000 you would write off 4,000 each year for 25 years. There are different methods of depreciation and you might need an alternate depending on the use of the building.
Just to verify
* Are you sure it's not 27.5 years or even 29.5 years (or is that commercial property), rather than 25?
* Are you sure on the 4%? This is privately-owned, fully rented out building containing 6 apartments. The owner doesn't live in it, although it is privately owned/administered, not company-owned/administered.