What do the Regulations say? This ain't good. They are sticking it to us. The regulations require that every business be able to separately establish that it rises to the level of a Section 162 trade or business, and that means big problems for landlords. There's not even a carve-out for real estate professionals under Section 469(c)(7), meaning even those who truly ply their trade in the rental real estate world will have to establish that the rentals satisfy the nebulous Section 162 standard.
The regulations provide only one exception, found at Reg. Section 1.199A-1(b)(13), which provides that if a taxpayer rents or leases tangible or intangible property to a commonly controlled trade or business (a self-rental), the self-rental activity is treated as a Section 162 trade or business.
https://www.forbes.com/sites/anthonynitti/2018/08/09/irs-provides-guidance-on-20-pass-through-deduction-but-questions-remain/#4e9cd1602ff8