Calculating operating expenses

[Dan Bottiglieri]

When you are finding your monthly net cash flow, are property management, maintenance, utilities, capex, etc percentages of gross rent, or percentages of your gross cash flow (net rent - PITI)? I usually say 8% for pm, 5% maintenance (depending on the current state of the property), 5% capex, etc but should those be a percentage of gross rents, or gross cash flow?

Thanks a ton!