You probably do qualify for QBI with four rental properties. While it's possible you would not, I would be surprised if you did not. See Revenue Procedure 2019-38 at https://www.irs.gov/pub/irs-drop/rp-19-38.pdf if you want some kind of confirmation. Just keep in mind that the "trade or business" classification is for QBI purposes ONLY, and nothing else. The income, expenses and losses are still passive for just about all other purposes.
I myself have three rental properties and just flat out do not qualify.
