Landlord
Whoever owns a home and leases it to someone else for rent is its landlord. The rent step of BRRRR makes the investor a landlord, with legal duties on habitability, deposits, fair housing and notices that apply whether the investor manages the property or hires a manager.
Landlord-tenant law is mostly set by states and cities, and it varies a lot: deposit limits, required disclosures, entry notice, repair timelines and eviction procedures. A rehab that brings the property up to code helps with the habitability side from the first day.
The default deal budgets 8% of rent for management and 5% each for vacancy and maintenance. Investors who self-manage keep the management fee but take on the calls, showings and bookkeeping. Lenders often still count a management expense when they review the rent.
Further reading: Landlord on Wikipedia.