How do you consider equity build up when analyzing a property?

[Roochita P.]

So many calculators I've seen ignore equity build up. Why is that? Is it because that equity is locked in the property and not available to you? 

I just think it's crazy to ignore the fact that somebody else's money is paying down your mortgage (interest AND principal). When you sell the property those principal payments become money in your pocket. Why wouldn't you factor that in? Most people use pure cash flow analysis for calculating after-tax returns, but in my opinion it ignores a huge part of the value of leveraged real estate investing. 

What am I missing? The practical implication for me is that I will look not only at traditional cash flow numbers (cash-on-cash, before tax, after tax) but I will also then factor in equity build up when generating a "complete" or "comprehensive" return. Maybe there's an actual word for that.