Do you see a crash every 18 years in this chart? 

The papers had a chart with the horizontal heading "Average monthly rent" for a 835 sq. ft. unit across the top and on  the left  vertical side was the exit CAP rate  (36 month hold). 

So neat and precise. 

(See charts below.)So, I tell buyers ...

Yes. that's precisely what he's selling. 

A closer look reveals a concerning trend of decline in hours worked over the past few years, as depicted in the chart.

Specifically on whether the high interest rates will lead to an increase in mortgage delinquency rates similar to what we saw during the 2008 great financial crisis.I plotted the chart below (Figure 1) to compare Fed Funds rate to unemployment rate and mortgage delinquency rate. 

You need to develop a Scope Of Work that is precise and then start getting prices for all the work.Once you have that magic number, then you will add that to the cost you pay for the house, along with any other fees or expenses...Then look at finished Comps (get a Realtor like @Chris Ayars said) and see if you will make any money......

There is no precise formula by which properties are placed into classes, but here is a breakdown of the most common classes, A, B and C:Class AThese properties represent the highest quality buildings in their market and area.

Its a long game and if done with precision eventually you will have vast financial freedom.