When I teach my multifamily investing workshop for a couple of days, by the end of it my students know who their best friend is:
NOI! Or Net Operating Income!
That's not your net cash flow. I'm talking about the income generated from operating the apartment building (income minus operating expenses) before you service the mortgage. Your net cash flow is the money left after you have paid your mortgage.
NOI is a multifamily investor's best friend because every time you increase the NOI, there's a huge BIF LIFT EFFECT or WEALTH MULTIPLIER EFFECT, that is the value of the property increases exponentially.
One of the ways that you can increase the NOI is by successfully appealing your property tax assessment if you feel the municipality has over-inflated the value of the property and therefore has inflated your tax bill.