So what happens is there is a differential that builds up over time where you get grand-fathered into a lower taxable value.  

Maybe they have a lower percentage of owner-occupied units, insufficient contribution to reserves, or some lingering issues.

Single-Family Home with a Basement:Pros:Familiar single-family living with potential rental income.Can be a good starter home, quieter living if the basement is well-soundproofed.Potentially lower initial investment compared to a duplex (depending on renovations).Cons:Finding tenants might take longer, especially if the basement isn't a fully formed apartment.You'll be responsible for all maintenance and repairs for both units.Less separation between your living space and the rental unit.Multifamily Duplex:Pros:Clear separation between your living space and the rental unit.Potentially higher rental income with a full, separate unit.Faster tenant search as it's a more traditional rental format.Cons:Might be slightly more expensive upfront than a single-family home with a converted basement.Potential for noise complaints if the duplex isn't well-built.Dealing with potentially two sets of tenants (though vacancy rates are typically lower with duplexes).So, which one to buy first?

Good data is more expensive and there's no way around itIncomplete data sets - if you're only getting a few phone numbers and a few email addresses you are missing out on deals.

In my house I have a Maax which has the tub and lower part of the surround as one piece and then a second piece of the surround is added higher up-so it eliminates that join where the edge of the tub meets the surround where water tends to pool. 

We would like to keep the operating revenue and expenses separate from our personal stuff but want to file them along with our personal tax returns.

There's no mention of your income, monthly expenses, DTI, risk tolerance, goals, etc.

I did however put into their lease that if the lawn ever became neglected it would immediately be taken over at their expense by a company of my choosing.

Are there any other expenses that I should be accounting for or any way to verify that what I'm analyzing is a solid deal?

A lot of of TK providers 'inflate' their numbers or show higher returns because they don't factor in things like leasing fees and other expenses.