**Net operating income (NOI)** is a property's rental (or program) revenue minus its operating expenses — **before** debt service and capital costs. It's the building's own earning power, independent of how you financed it. - **In:** rents, parking, fees — minus property tax, insurance, utilities, maintenance, management, porterage. - **Out:** mortgage interest and principal, depreciation, capex. Those belong to the capital stack, not to operations. NOI is the hinge of real estate math: divide it by a [[Cap rate|cap rate]] to get value, divide it by total cost to get [[Unlevered yield on cost AKA cap rate (UYOC)|yield on cost]], and subtract debt service from it to get the cash flow that actually reaches investors. Related: [[Cap rate]] · [[Unlevered yield on cost AKA cap rate (UYOC)]]