Again a real reduction in tax over the same profit.How about the principle repayment paid for by your tenants. 

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.

I guess dust is not settled yet...I hear that everyone is saying it's case by case...and everything is negotiable!!!

That was the entire premise behind raising the FFR - to slow down economic activity by making financing more expensive. 

What I mean by that is, lower rent units need higher capex and maintenance reserves.  

Podcasts like Bigger PocketsBooks like Rental Property Investing by Brandon Turner are great startersGet to some events and meetups to gather free info and meet folksLet me know if I can be resource for you! 

Unfortunately, the path you take is not always by choice.

My assumptions based off research is I will be able to deduct 1/2 of all allowable expenses based off the ADU square footage (My understanding of that list below)  1/2 Mortgage Interest (Not principle) 1/2 Utilities 1/2 Property Taxes 1/2 Insurance (assuming I don't have separate ADU insurance)  1/2 general house maintenance (depending on the issue and if it's related to the ADU)  1/2 Depreciation (Home value, not land divided by 27.5)  KEY QUESTION: If my mortgage (PITI) is $5400, and all of those ADU deductions equal $3800 monthly, and my ADU income is $1800 monthly, am I allowed to pay the difference in "deductions" from my real estate business income? 

Here's some guidance on buying your first investment property in Southern California or Columbus, Ohio:Down payment:For investment properties, lenders typically require 15-30% down payment on your first investment15% down is possible with excellent credit (700+ score)20-25% down is more common, especially for multi-unit propertiesSection 8 considerations:Pros:Guaranteed portion of rent from governmentPotential for longer-term tenantsMay be easier to fill vacancies in some areasCons:More paperwork and inspections requiredRent amounts set by local housing authorityPotential property damage concernsOther tips:Research local markets carefully - price trends, rental rates, etc.Factor in all costs - taxes, insurance, maintenance, vacanciesConsider starting with a single-family home or small multi-unitBuild a team - real estate agent, property manager, contractorsHave cash reserves beyond just the down paymentUnderstand landlord-tenant laws in your chosen locationI'd recommend talking to local real estate agents in both areas to get more specific market insights.

., does zoning allow for short-term rental use or would a future owner be at risk of it getting shut down by the city).