We bought a house in 1978 and lived in it until 2012. We turned it into a rental at that time and rented it until 2021 and sold it. In 2015 it was turned into a business rental since it had been rented for more than 3 years. What figure do I put in for the purchase cost of the house? What we paid in 1978 or what its value was in 2015 when it was converted into a business property?
