Cash flow is the money left over each month after you have paid every expense related to the property. Gross rent minus your mortgage is not cash flow. That calculation leaves out half the costs. Here is how to do it correctly before you buy.
The Formula
Monthly Cash Flow = Gross Rent - Total Monthly Expenses
Simple in concept. The work is in making sure you include every expense. Most investors who buy bad deals missed something in the expense column.
What to Include in Monthly Expenses
Mortgage payment (PITI). Principal, interest, taxes, and insurance. If your lender escrows taxes and insurance, this is your full payment. If not, add property taxes and insurance separately. Use the actual payment, not just principal and interest.
Insurance. Landlord insurance costs vary by property type, location, and coverage level. For a single-family rental, budget $75 to $200 per month as a rough starting point. Get an actual quote before you close.
Property management. If you use a property manager, budget 8 to 12 percent of monthly rent. On a $1,800 rent property, that is $144 to $216 per month. Even if you self-manage now, model it in. If you ever want to stop self-managing, the deal should still work.
Maintenance reserve. Budget 1 percent of the property's value per year for maintenance and repairs. On a $200,000 property, that is $2,000 per year or about $167 per month. This covers routine repairs, appliance replacements, and the small things that add up. Some investors use 10 percent of monthly rent as a simpler rule of thumb.
Vacancy reserve. Properties are not occupied 12 months a year. Budget 8 percent of annual rent for vacancy. On a $1,800 rent property, that is $144 per month. Over a year, it covers roughly one month of vacancy.
HOA fees. If the property is in an HOA, include the full monthly fee. These can range from $50 to $500 or more depending on the community.
Utilities if owner-paid. Some properties include water, trash, or lawn care in the rent. If you pay any utilities, add those costs.
A Simple Example
Property: single-family home, purchased for $220,000. Rent: $1,900 per month.
Expenses: Mortgage payment: $1,100. Insurance: $120. Property management (10%): $190. Maintenance reserve (1% of value / 12): $183. Vacancy reserve (8% of rent): $152. No HOA, owner pays no utilities.
Total expenses: $1,745 per month. Monthly cash flow: $1,900 minus $1,745 equals $155.
That is a modestly positive deal. Not spectacular, but it cash flows. A buyer who only looked at rent minus mortgage would have seen $800 per month and thought this was a strong performer.
The Most Common Mistake
Forgetting maintenance and vacancy. These are real costs that show up on a long enough timeline. Skipping them makes every deal look better than it is. You are not being conservative when you leave them out. You are setting yourself up for negative surprise.
What Positive, Neutral, and Negative Cash Flow Mean
Positive cash flow means the property generates income above all expenses. The property is adding to your monthly finances.
Neutral or break-even cash flow means expenses roughly equal rent. You are building equity and potentially benefiting from appreciation, but the property is not adding monthly income. This can be acceptable in high-appreciation markets. Know what you are buying.
Negative cash flow means you are paying out of pocket each month. The property costs you money. Some investors accept this in strong appreciation markets. Most should not, especially starting out. Negative cash flow is not a strategy for building financial stability.
Insurance Is One of Your Most Predictable Expenses
Unlike maintenance costs that vary month to month, insurance is a fixed annual premium that you can model precisely. Get a quote before you close on a property, not after. Insurance costs affect cash flow, and in some markets or for some property types, the premium is higher than buyers expect.
Run the Numbers Before You Buy
Use a calculator to model it out. Run the numbers yourself: investorpropertyinsurance.com/rental-profit-calculator
Buying a rental property? Make sure insurance is part of your plan.
Start here: investorpropertyinsurance.com/get-a-quote