But I find risk and future uncertainty very hard to quantify.

We negotiated based on our knowledge of the market, the inspection report, and quantified items that needed repair or replace.

In order to quantify rents I checked Zillow, Craigslist, etc and subtracted a couple hundred off of what 1 and 2 bedrooms were asking there in the area.

I would run the numbers then like the property is vacant and has no income and the numbers cannot be verified from what is stated but that is just me.If I can't quantify and verify something to be true then there is a huge risk and unknown going into a property.

COC return quantifies how much you will get paid while waiting.IRR is a useful measurement because it is the definitive calculation for comparing one investment to another (NOT cap rate!)

As it is important to save a $, you have to be careful not to spend every waking hour working the process, only to realize that you haven't saved much to quantify your time, and still have to complete the project! 

Well, it's not whether or not I have the stomach for it, etc, I'm trying to quantify the impacts, (in sole regard to this title thing) get probabilities of the risks, the triggers, mechanisms and procedures, etc. so I can make a proper risk management assessments, backup plans, etc.

Not all of the possible market knowledge can be quantified though in simple things like price per square foot or differences in rent.  

There is another aspect of investments that is rarely discussed because it's not quantifiable so it's difficult to measure.

The cycle of this and length of time varies by local market on a micro scale and then also by national factors on a macro scale.When the markets recovers these high appreciation markets attract speculators that drive prices up.When they also leave the market it drives prices way down.So California,New York etc. you have wild swings in value whereas say in Georgia we slipped in value as well but prices were not as extreme.Investors like cash flow because it is an immediate quantifiable income.Appreciation is a crystal ball speculative investment that you hope grows faster than inflation every year.I will say there is only so much land to build on for high density areas.So if you make a bunch of money at your job and have reserves than it could be a great long term appreciation play plus rents could rise at a fast clip.You have to remember every investor has a different plan.The investors who are my clients think differently based on a different set of goals and how they want to allocate time.