Figuring out the asset value

[Emily Wilson]

Hi,

I am new to real estate investing.  In order to determine if a house is a good investment or not, we created a spreadsheet that incorporates the recapture tax as part of the calculations.  The problem is, you need the value of the house/improvement in order to do the calculations.  Listings have the property tax land and additions value.  I was using that originally.  However, it occurred to me that when a house is sold, they reassess it and the additions value will likely go up making my calculations inaccurate.  

1) Am I thinking about this correctly?

2) If I am, how do I figure out the value I need to use?