Investment means the value of qualified property incorporated into or used at the qualified location or locations. For qualified property owned by the taxpayer, the value shall be the original cost of the property. Improvements to real estate qualify as investment even if the entire improvement is not finished or ready for use. The percentage of completion of the improvement determines the portion of the investment that has occurred for any given year. For qualified property rented by the taxpayer, the average net annual rent shall be multiplied by the number of years of the lease for which the taxpayer was originally bound, not to exceed ten years. The rental of land included in and incidental to the leasing of a building shall not be excluded from the computation. For purposes of this section, original cost means the amount required to be capitalized for depreciation, amortization, or other recovery under the Internal Revenue Code of 1986, as amended. Any amount, including the labor of the taxpayer, that is capitalized as a part of the cost of the qualified property or that is written off under section 179 of the Internal Revenue Code of 1986, as amended, shall be considered part of the original cost.