It's a much less comfortable home life, but it sets you up to make a great return with less risk. 

I believe that you don't get returns (failed to deliver) with bulk mailers so you don't know which addresses are bad.That's the simple stuff.My advice is to do various mailings that you or some prepares locally, that go out immediately, using 1st class postage.

Credit Rating/Bank Statements/Tax Returns: Specify your requirements, if important to you.Purchase Criterion: How do you define a good deal, which will be profitable for your borrower and safe for you?

You are not even scooping your initial investment so your cash on cash return is negative.

I just don't know how well it would work since I already have all the entities and would just need advice, consulting, cleanup, and filing returns, that's pretty much it!

This implies your return numbers are inflated.  

Leverage magnifies return. 3) The effort involved in adding an ADU is comparable or larger than a rehab associated with a BRRRR.

You get a Capitalization Rate (CAP Rate), which equals your annualized return by dividing the Net Operating Income (you had gross in your narrative) by the purchase price.

million in addition to their investors (who expect a reasonable rate of return) by keeping the rental rates at a fraction of the market rate?

Many of which are savvy BP type clients who are doing updates/raising rents and then the buildings do cashflow positive even with lower down payments which produce amazing returns (at 3.5-5% down you get close to a 50%+ return a year just off mortgage paydown).