Yes, the cost basis for your mother would be 50% of the original cost, purchase expenses and any capital improvements before the death of your dad. Next she would add, on the date of death, 50% of the fair market value (FMV). She is entitled to 50% of the stepped up basis in 2004. Any capital improvements made after 2004 would also be added to the cost.
Land is important as well. You can use the tax assessment from the county or city to arrive at the percentage of cost that applies to land. When you enter the rental asset, enter the entire cost of the rental house and then enter the land cost where indicated. TurboTax knows to reduce the entire cost by the portion that applies to land before depreciating. Land is always an appreciable asset and will have much better tax consequences at the time of sale in the future.
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