We once replaced the cracked single pane window in a kitchen, because that was the worst one in the apartment, and the day that it was installed the tenant asked us why we didn't replace his bedroom window first, because it was blowing cold air on his head when he slept.  

GRM is the worst indicator of them all :) But, you knew I was going to say that, Bob..lol

You have, in essence, asked "teach me how to perform neurosurgery" and many of your assumptions will be incorrect (thus making you your worst enemy!).

Couple of quick items:These guys usually sell their worst properties first.

but BPers tell me that they benefit a lot from me sharing my mistakes.Also in my podcast - http://Biggerpockets.com/show65, I share the worst investment mistake I made in my real estate career.

More recently, in Texas I took the Kaplan courses on Promulgated Contract Forms, Law of Agency and Contracts.The textbook for the Promulgated Contract Forms course had some of the worst writing I've seen.

For good deals you have to find the properties in the worst condition, but in a good area.

I have known couples that have as much as gotten divorced over the experience and results of their construction projects and also seem people go bankrupt or simply go through the worst experience of their life leaving them concluding that they will never not ever attempt construction projects ever again. 

Some did multiple tours.In 2008 we were faced with the worst recession since the Great Depression.

I'm sure this will hearten landlords everywhere...http://www.businessinsider.com/buying-a-house-was-the-worst-financial-decision-i-ever-made-2015-6