A rental activity is a passive activity even if you materially participated in that activity, unless you materially participated as a real estate professional.
https://www.irs.gov/pub/irs-pdf/p925.pdf
Additionally
The following aren’t passive activities.5. Rental real estate activities in which you
materially participated as a real estate professional.
Am I to understand that if I become a Real Estate Professional, then I can treat my properties as non passive and offset against my regular income?
If you qualified as a real estate professional
for 2020, report income or losses from rental
real estate activities in which you materially participated as nonpassive income or losses
