How do multi-unit buildings work?
When you add a duplex, triplex, or apartment building, the wizard asks whether you own a single unit or the entire building.
If you own the building, each unit gets its own rent, tenant, and lease. Property pages let you switch between the whole building and a single unit, so budgets, rent history, and expenses can be viewed per unit.
Building-level costs like the mortgage or insurance stay at the building; unit-level items like a lease or a repair in one unit are tagged to that unit.
Once a property has more than one unit, every tenant you add must be assigned to one. The unit is what keeps each tenant's maintenance requests private: a tenant sees requests for their own unit and their own lease, never a neighbour's.
You can turn a single-unit property into a multi-unit one at any time from the Units tab on the property page - useful if you start renting rooms of a house separately. Give each room its own unit and its own lease, and the tenants stay separate.