Those who have invested I am sure can chime in. 

Verifying last 2 years of rental history and income extremely important to find the “best of the worst”.Make sure you understand the Class of properties you are looking at and the corresponding results to expect.

For the BRRRR process I plan on using a hard money lender for the rehab process for the SFH's but what I'm not sure of is, should I purchase a duplex and rent one unit out and live in the other or should I just rent for now, not purchase a duplex and just purchase a SFH with cash and start BRRRR'n immediately?

Sure, sent! 

Who makes sure it’s clean (your regular cleaner?)

These areas tend to provide the best balance of affordability and rental demand.That said, Detroit’s market is unique.

How does the already deep in debt CA afford to tack on $50 BILLION in debt service?

I also invest in other assets such as stocks, and private companies as well. for RE agents I see absolutely no conflict.. its their job.. not every agent starting out can afford to buy a rental.. and note very agent even wants to own a rental ( like me) I only like to deal in land when I sold RE to the public .

Just make sure you screen, screen, screen. 

Sure, because when you take rent payments out of the equation you can focus on the tenant landlord relationship and providing the best experience for the tenant.All the best!