Be interested in what your thoughts are to include this in a lease (needs to be maintained to some defined degree of cleanliness rather than waiting until move-out and deduct cleaning charges from their deposit).

For example, you can deduct mortgage interest, property taxes, operating expenses, depreciation, and sometimes even travel expenses related to property management.

My CPA says STR "A" can only deduct expenses for STR property "A", and only up to income level.

What if there are already damages to the property that you could have deducted and tenant keeps whole thing rather than submitting to new management? 

If you can invest at a higher return than your interest rate, I'd refrain from paying it off so you can continue to reap the tax benefits of deducting mortgage interest from taxable your rental income.

One benefit you may want to take advantage of with the 401k is the tax deduction. 

I am pursuing my goal to be a land investor, and so far I feel good about having bought a number of lots at a good price. There is still a lot I have to learn, so my question is going to be as basic as it gets.  I nee...

So, you don't necessarily have to complete the separation of units by January 1st to start deducting expenses.Facts are important but overall, think of the place in date as the date you can start to deduct some of these expenses. 

How are you going to deduct mortgage interest, depreciation, property taxes, insurance, etc on the cottage tied to your primary home - without getting flagged for an IRS audit?

For example, for rental properties, lots of the categorization depends on the REI's specific tax strategy regarding what we're capitalizing versus what we're immediately deducting.