The other portion of your question and getting down to the tax benefits of it are going to be best addressed by a CPA yes, as you're going to be going off of a % base or SqFt base and it sounds like it isn't a true 'duplex' equal down the middle in terms of sizing- to then split your deductions 50% down the middle would fall into the real of we don't go there and mess with Uncle Sam that way and stay out of trouble.

I have spent the last 3 months reading and listening to the bigger pockets podcast, I will be purchasing income producing multi family properties and ideally would like to take advantage of the BRRRR method.

You'll get people that never leave them because they are afraid they're calling DNC lists and will get in trouble and you'll get people that always drop one because they might get a call back.When I'm calling homeowners I do leave a VM and the best for me is simply, "Hi, my name is ______ . 

.- I was able to get approved for access to private investigator software to find the true owners of these properties since conventional skiptracing produced poor results.

Your thoughts are about to get you into some legal trouble.

It'll save yourself some trouble down the road when a tenant needs an oven, etc.

Here a quick tip for when you are interviewing companies ask them this question "what are you steps to address a broken hot water tank"If they answer, send a plumber out and address the problem, you know they'll charge you an arm and legIf they say, they'll walk the tenant through trouble shooting steps like resetting the pilot light, you know they'll save you money 

I am having trouble understanding how to appropriately evaluate the property's value - is it based on the current "market" value, the 2020 tax assessment value of land and improvements, or from a bank appraiser who would be used during the purchasing process?

.#3  You may want them to go do a quick visual inspection of the house before you make your offer....they may be able to keep you out of trouble before you even get started.#4 They can provide you comps for both the purchase and rents, and perhaps verify rents for you of current tenants.#5  They may be able to provide location expertise and inside knowledge of the area for you....the good, the bad, the ugly.   

If I had the portfolio and the experience I would be much less nervous, but I can't shake the feeling of buying a property in my first year then boom, crash happens, I can't find tenets, finances are in trouble, etc.