Understand that property improvements done after you owned the property do add to the cost basis. it "does" "not" "matter" if the property was classified as a rental or not. It still adds to the cost basis of the property.
Other expenses such as repairs, maintenance, utilities that were incurred while the property was *not* classified as a rental are flat out not deductible anywhere at all on the tax return. They are just personal expenses same as buying groceries at the supermarket.
