How to calculate depreciation on residential rental property

[Johnson Lo]

Hi Bigger Pockets,

This is my first time posting on the forum.  I plan on purchasing my first rental property this year!  I plan on going the turnkey route of purchasing out of state property.

I had a question on calculating depreciation on a residential rental property.  I've heard that I can depreciate the building portion of the property for 27.5 years.  Do I rely on the county assessor to help determine the value to depreciate or do I calculate it myself?  If it is based on the purchase price, what goes into the purchase price?  Does that include closing costs and home inspection costs? 

Thanks and much appreciated!