My goal is help REIs avoid many of the predictable rookie traps that lead to bad experiences and financial disasters. 

It’s impossible to predict the next real estate crash; just like stock market, those who say they can, are 100% full of crap. 

The reason why I suspect it is not taught, it is not considered a reliable metric to predict future profits. 

I predict a lot are getting in over their heads

I’d have a pro do an inspection and estimate You are basically asking a crystal ball question.... no one can predict the exact future of the roof..... it may last you years with no issue or it may leak in the dead of winter and cost you 3x as much .... no one really know.

- If you're going to do this you'll have to develop a metric to predict the next crash.  

If you ask renters and potential home buyers in Sacramento, they'll tell you prices are too high and many predict a crash.

Get a full understanding of the surrounding properties and what they charge for rentals to help better predict your cap rate. 

If rates go up as I'm sure they will (demotivating buyers)... but at the same time there are more buyers in the market it seems hard to predict or even estimate if buyers will actually be there to purchase a flipped property for a decent profit within the next couple years, especially if that property is purchased in today's market! 

So you naturally can get a little bit of accidental (but predictable) blind leading the blind.