It will be difficult to generate those kinds of returns in your own small multi-family without leverage.I think you are overstating both the cost and complexity of taxation on Unrelated Debt-Financed Income. 

If you do need to file and pay sales tax, you can do so with the Ohio Department of Taxation here.

It allows you to claim the rental income at a lower taxation level and also validates your tax position of being a "full-time real estate professional."

- how you ensure my proposed structure is accurate, flexible and relevant, so that aren’t any things that will come down the road and increase my taxation, or possibly hurt overall ability to further engage in business planning? 

Couple of things for you to consider.If you're thinking to move as well you'll want to take a look at state taxation. 

You not only have to be concerned with "THE MAN" (IRS), you have to be concerned with "the man" (State taxation). 

With the recent increases to standard deductions - the taxation benefits of owning your own home have been reduced.Being a landlord continues to be tax effective.I have a family member who is looking to buy for themselves personally - but I am helping them with down payment.

It's still breaking the rules, so consult your own conscience.The other issue is taxation of the refi cash itself.

except in VERY specific and limited circumstances, running rental through an S corporation adds an additional layer of complications and MAY cause more taxation.  

It's another unneeded layer of "taxation" and "regulation" that we don't want to deal with.