At that point you're going to need to pay rent to the investor which basically kills the entire concept of a house hack.In a city like Boston, notwithstanding COVID, you can even house hack a condo.

I have been interested in the concept of using a cosigner but havent heard anyone talk about it yet.

That is very annoying, as its a pretty clear concept. 

In my opinion, though, a well renovated older home on a larger lot gives you more options in the long-run of property ownership, while newer construction gives you a simpler, lower-maintenance operation in the short term.If I'm buying and holding a property for the long run, I prefer well located homes on ideal lots, which tend to be older homes in my market. 

Approval process is much simpler and the appraisal is based on the ARV and scope of work to be performed.

I understand (mostly) double-entry accounting concepts, and I have most of my transactions recorded (just using Google Sheets for now) with a debit account and a credit account.

Although the BRRR is nothing new its a very very old concept and has been done for generations.. its just a coined term on BP to sell books nothing magic about it.. 

He even admit on several occasions that most of his writings in the "Rich Dad" series are fictionalized accounts designed to teach concepts. 

These branded concepts are quite similar but more focused on the use of Whole Life Insurances that are one subset of the permanent life insurance arena.

I am exceptionally new to real estate and am not familiar with most concepts and terminology, so thank you for your patience!