Establishing Rental Cost Basis

[Ian Alli]

I purchased a home in September 2003. I lived in this home until May 2015, which from this point forward, the home was converted to a rental/service property. 2015 will be my first year filing taxes with having this rental property. I am trying to establish my cost basis for IRS depreciation purposes and I am stuck on figures. My local (San Diego, CA) Property Tax documents reflect numbers that don't quite seem right when I look at the breakdown of Land value when compared to the Improvement value. The Land (5100 Sq. Ft. lot) is valued at $313,405 and the Improvements are at $76,895. I know I will have to subtract a dollar amount for personal usage since I lived in the home for 12 years. How do I calculate that figure? Also, how do I establish a cost basis to maximize the depreciation amount annually? Those figures just don't seem right. It almost seems reversed. Any help or advice is greatly appreciated as this is all new to me. I don't want to start out on the wrong foot. Thanks in advance for your input.