With the SFH market being driven by irrational home buyers the cost per door is highly unpredictable down the road.

The best way IMO to combine ALL sources of profit into a single analytical framework is to project out the financials and planned exit and calculate the IRR ... this is still far from fool proof, but at least it allows you to look at BOTH cash flow AND appreciation, and other factors in combination, and not in isolation and fixed forever in time as with CoC, CAP rates, etc.Also, both cash flow and appreciation are not steady, and not linear ... they both go up and down over the short term in unpredictable ways.

This is absolutely unpredictable.  

The lawyers I have spoken with don't seem to understand exactly what the laws are in my situation, and they have told me that the magistrate court is unpredictable and that the judge basically makes the decisions instead of the laws.

If loan goes over into workout/default or foreclosure the payoff date quickly become unpredictable. 

Unpredictable. 

I think rates will stay low...Home Prices - Is there a risk of volatility in home prices with an unpredictable person in office?

We are experiencing heat wave right now in LA (and other areas in the state and in the country), where the A/Cs are not totally efficient. Some areas have even experienced power outage during the most part of the week...

Condo's are generally a poor option for investors due to unpredictable HOA fees and special assessments.

Those aren't fun balloons to pop...I think a lot of people miss that cap-ex expenses can be unpredictable.