Defining a trade or business is easy for the most part, however certain activities are murky and one of them is rental properties. On one hand an argument that rental property income is already tax advantaged can be made since it is not subject to self-employment taxes (Social Security and Medicare). However, if it were subject to SE tax, people would simply create management entities, elect S Corp status, ding the rental a management fee and achieve a Section 199A deduction that way. This is perhaps one reason the IRS isn’t raising a big stink on rental properties.
Also, in Commissioner v. Groetzinger, 480 U.S. 23 (107 S.Ct. 980, 94 L.Ed.2d 25), the U.S. Supreme Court in 1987 held that for an activity to meet the definition of a trade or business it must be engaged to a) earn a profit and b) with some regularity and continuity. This is also most rental property owners, even if it is just one house.
And… don’t read too much into the words “earn a profit.” This does not mean it must earn a profit… but your intentions for conducting the activity is to earn a profit. Whether you earn a profit or not does not necessarily alter your intentions. Make sense? In other words, “I wanna earn a profit. I’m doing all the right things to make a buck, yo, but right now times are tight and this depreciation thing is killing me.”
So, as of right now, rental property owners are able to calculate and use the Section 199A qualified business income deduction. This is also where depreciable assets come into play for determining the Section 199A limitations. No, you do not need to pay a W-2 salary from your rental property to enjoy the qualified business income deduction.
Taxpayer's Comprehensive Guide to LLCs and S Corps : 2019 Edition