For the first handful of investment properties I purchased I had a similar spreadsheet but instead of life span I had expected years to replacement.

You have to get a life-span for each, and than a estimated cost of replacement, figure out where your current age is, and than you know the estimated time left to replacement.

Your just NOT going to get  20% returns in a span of a week/month in real estate.

I look at the appreciation rate that spans down cycles and come to almost 6% (4.7% for this century that includes the Great Recession). 

ZIP codes are rather random and large and many of them span across vastly different neighborhoods and price ranges.What you can go by is price ranges.

So you need to know where you are in the life span of those items as you work a place up. 

It's one thing for us to own one and take good care of it so that it lasts, but adding renters to the mix will inevitably shorten their life span even more. parking is another issue.

Most of the area only had 8-12” over a 48 hour span.

The data I am going to present spans back to 1968.

Most years my cash flow exceeds depreciation by a significant amount.Standard depreciation helps reduce the tax but the reality is the existing components at purchase have a life span and the standard depreciation is to cover those costs.