Great & interesting history, thanks so much for sharing.

They offer a range of services from just a basic credit check, to a more advanced income check and criminal history search. 

If you rented by the room, then no - Conventional typically does not allow for boarder income in properties that have not yet been placed into service (meaning you dont have rental income history on a tax return for that property).

In 18 years (the time it will take for my daughter to grow up and go off to college) that $12k I saved by putting in a bunch of work will yield $78K.

Past operating history is irrelevant.  

There are properties that probably have 2X-3X the cash flow my properties have and are comparable in price but given their location and tenant history attract a much worse group of tenants and have much higher expense ratio relative to repairs and maintenance and general wear and tear on the property because of the type of tenants they attract.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

I decided to get a remote job, establish work history, save up enough capital for my first househack while I researched and learned about markets and strategies.I'd like to create an active business and I am looking at the MTR strategy.

(is there any reviews or history on his business online)The inspector that said 70+ is probably one of those everything needs to be replaced don't risk type, however will probably be the more expensive guy.

I work hard but I spend twice as much time with my daughters every day.