My wife is a 1st grade teacher, and I've worked for my families earth moving/construction company my whole life.

As long as ALL your tenant applicants are being graded on this SAME criteria then you are in compliance.

In general even in cash flow markets they were often D grade assets. 

Check out The Ultimate Guide to Grading Cleveland Neighborhoods before spending any money on a BRRRR deal.

Hey, I can send you a link that has the neighborhood grading of Cincinnati.

In the beginning, I chose to try to buy the high interest high risk loans ( C-F credit grade, 15%-28%+ ).

Using age as a guide to class is more accurate with garden-style Multifamily apartment complexes and that is the context of my previous answer as it is in Multifamily and commercial where you most commonly see the letter grade system.  

Now I'm curious, assuming these rooms are below grade, are there acceptable window well parameters for egress?

Standard grade tiny typically sells for $30k - $50k though many people build their own.

@Alex SanfilippoFor door locks I would go with commercial grade to withstand the abuse.