Definitely the "quantity over quality" adage applies to Facebook.

Be patient and consistent on your quantity of making offers.

To answer your question specifically, look for loose or curling shingles, discoloration, particles stripping from the shingles and falling in the gutters (they look like tiny pebbles), streaking, or roof leaks inside (a very late sign). 

In another home my tenant refuses to pay the $200 / mo water bill,  thereby cancelling out my tiny cash flow profits and i have to pay it.

Ohio properties cash flow a tiny bit more for me.This is my personal experience with 6 properties, purely anecdotal

They take some technique or strategy that’s only workable or beneficial in a very tiny percentage of situations and generalize it as a major breakthrough.  

I had moved to New York City at the time and had a tiny closet with no windows as my office.

(Tiny old postage stamp lots)in parts of the bay area its mandatory to change the drain line when houses are sold if they are a certain age and still clay pipe.. my brother in law does a ton of them.. realtors are his source.. many times they just pipe burst.. and are done in a few hours for 6 to 8k. when I was doing my rental thing in the deep south we could get a new PVC from house to street 50 ft or so for 1500 or so.. if we did it during rehab and not under stress.. 

Increase portfolio by 100 units (a combination of a tiny home community in Florence, Arizona, a condo development in San Tan Valley, Arizona, a few multi-family properties and or mobile home parks, and 20-40 single family residences in Arizona and the triad area of North Carolina - mostly Greensboro and Winston-Salem).2.

The reasons for investing are much more than just cashflow, that is 1 tiny tiny part. 1.