A 1% rise in borrowing costs will equate to a 20% fall in home prices.

Of course in real world scenarios any of these numbers could be up or down in either direction, but I’m just using this is a rough base for this equation.

I'm also not diminishing what a good realtor can add to the equation for people that really need help and guidance. 

This is the part where we talk about the importance of “owning the relationship” with your guests, not letting a platform, with an algorithm that can change overnight, control the equation. 

It has a $49,547.13 NOI equating to an 8.85 cap rate.

However in those areas where the houses are 30-40 now you will see homes at or under 10k meaning (in my opinion higher risk) out of the 104 rentals we have only 5 are in these lower price points and we have 4x the turn over and 5x the repairs which really screws up your equations.....

Generally speaking, how many yellow letters would equate to one deal?

Like @J Scott says, hiring a great inspector can change the equation in your favor.  

Well, okay, certainly there is some equation that will tell you the cost per lead for Zillow, right?

All the GC license allowed my to do was take the GC cost out of the equation.