My question is: what should the money flow be in order to maximize income and reduce taxes while following all laws? 

This amount would reduce your left over cash from $30k to $22k.Scenario B: Purchase home for $100k using 50% down. 

The "unleveraged return on investment" can be a lot higher than the purchase cap rate when you are increasing rents, reducing vacancy, cutting costs (or vice versa).I believe this is what you are asking and/or point you are making.

We work to make the tenant stays for long to reduce turn over rate.  

@Jonathan Jaime VelardeMy advice is to not reduce your retirement savings and instead find other ways to scrape together funds for investing in RE.

I'm looking to move to a few housekeepers that I can pay directly to reduce the overhead associated with the cleaning service.I've been pretty hands on and focused on keeping my places in tip-top condition with amenities with the goal of five star reviews, higher price point and higher quality guests.

We rent them completely separately and assign parking to reduce conflict. 

I try to allow pets every chance I get but find other ways to reduce my risk.

(3)  Would the foregoing strategy effectively reduce the net income of the company and thereby reduce the self employment tax (i.e., by making the interest on the loan ordinary income to the owner)?

It is a major part of the North American economy and very common where I operate my business.You make sure in advance that you are getting a reduced price to offset more than your tax credit would amount to.