If you use a dwelling unit as a residence and rent it for fewer than 15 days during the year, you don’t report any of the rental income; it’s tax free. But you can’t deduct any expenses as rental expenses.
A statutory term describing the cost used to determine your profit or loss from a sale or exchange of property. It is generally your original cost, increased by capital improvements, and decreased by depreciation, depletion, and other capital write-offs.