Get your taxes done using TurboTax

It sounds like you are not in the real estate business.  Assuming this is true, your rental property is a rental and is not business property.  The improvements made before the property became a rental should be added to your basis.  The closing costs for the original purchase and refinance should be added to your basis.  Also, make sure you add any rental losses over the years, if any, to the calculation of the gain on the sale of your rental property.