Looking at buying a duplex, (second property) and writing off the depreciation on the propertyAs this would result in a loss for the year, I want to see if I can deduct it against my w2 ordinary income. https://www.biggerpockets.com/...This article is helpful, but I can't find anywhere where it talks about what is included in a "Real Estate Professional."

Your gain will still be taxed as ordinary income at your marginal rate. 

I'm assuming you're a W-2 employee, so look for ways to add long term capital gains, appreciation, etc, and avoid ordinary income that will be taxed at your W-2 rate.

There is also a large, shared back patio and backyard, is it worth my time and money to split them up?

Just remember to always consult with an attorney before finalizing any legal documents that are out of the ordinary course of business!

I’ll probably be doing an accent wall in the spot that gets filled in where the garage door is at on the interior. the garage area has an access into the house and access out the back to the deck and hot tub and patio and side yard. 

@Albert Bui - corporations can have "preferred" stock that can benefit the stockholder differently than the ordinary stock.

This does not take into account if you have outdoor spaces, such as building/redoing a deck, patio furniture, hot tubs, pools etc.

If you have gains on real estate you may be able to offset it but it’s not something you can deduct from your ordinary income

And, fees are ordinary income, while promotes are (generally) capital gain.