What Is NOI — and Why the Seller's Number Is Usually Wrong
Net operating income is what a property earns after operating expenses and before debt service. It is rent and other income, minus vacancy and every cost of running the building, and it does not include your mortgage payment. NOI sets the value, the loan size and the coverage ratio, which is why an operator rebuilds the seller's version of it from scratch before making an offer.
The formula, and what belongs in it
Effective gross income minus operating expenses equals NOI. Effective gross income is the rent you actually collect, not the rent the units could theoretically produce. The difference between those two is where most bad underwriting starts.
| Counts in NOI | Does not count in NOI |
|---|---|
| Base rent actually collected | Mortgage principal and interest |
| Other income: laundry, parking, storage, pet and late fees | Capital improvements such as a roof or new windows |
| Vacancy and credit loss, subtracted | Depreciation |
| Property taxes, insurance, repairs, management | Your personal income taxes |
| Owner-paid utilities, turnover, snow and landscaping | Loan fees and closing costs |
| Administrative, legal and replacement reserves | One-time legal costs from a prior owner's dispute |
Two rules carry most of the weight. Debt service is never an operating expense, because NOI describes the building and not your financing. And reserves always are, because the roof is wearing out whether or not you set money aside for it.
A worked example, and the same building with the seller's numbers
This is an illustrative model, not one of my deals. A 10-unit building with $240,000 of gross potential rent and $6,000 of other income.
| Line | Amount |
|---|---|
| Gross potential rent | $240,000 |
| Other income | $6,000 |
| Vacancy and credit loss at 7% | ($16,800) |
| Effective gross income | $229,200 |
| Property taxes | $24,000 |
| Insurance | $18,000 |
| Repairs and maintenance | $16,000 |
| Property management at 8% of EGI | $18,336 |
| Owner-paid utilities | $9,000 |
| Turnover and make-ready | $6,000 |
| Administrative and legal | $3,000 |
| Replacement reserves at $300 per unit | $3,000 |
| Total operating expenses | $97,336 |
| Net operating income | $131,864 |
That is a 42.5% expense ratio, which is normal for a small multifamily building that pays its own way.
Now take the same building with the numbers a seller typically hands you. No vacancy allowance, because the building is full today. No management fee, because the seller manages it himself. No reserves, because nothing broke last year. Insurance at the premium the seller has carried for six years rather than what you will be quoted. That version shows $176,000 of NOI.
Nothing physical changed. Four assumptions did, and they moved NOI by $44,136.
Why that gap is the whole deal
NOI is not a reporting number. It is the input to every number that decides whether you can buy the building and what happens after you do.
| What it drives | At the real $131,864 | At the seller's $176,000 |
|---|---|---|
| Value at a 7% cap rate | about $1,883,000 | about $2,514,000 |
| Loan supported at 1.25 coverage, 7% over 30 years | about $1,321,000 | about $1,764,000 |
The seller's four assumptions produce roughly $630,000 of imaginary value and about $442,000 of debt no lender will actually fund. An investor who offers off that number is not paying too much by a little. He is bringing $442,000 of equity he had not planned for, or he is not closing.
The lender's half of this test is in What Is DSCR, and Why 1.2 Is the Line. What happens when the appraisal and the market disagree about the result is in an appraisal is an opinion, the market gives the verdict.
Where a seller's NOI is usually wrong
Vacancy is missing
A rent roll shows the building as it is on one day. Underwriting needs an allowance for the days a unit sits empty, the tenant who stops paying, and the concession you give to fill a slow unit. Full today is not full all year.
Management is free because the owner does it
If you will hire a manager, the fee is an expense. If you will manage it yourself, your time still has a price, and a lender will underwrite a management fee whether or not you intend to pay one. Leaving it out is borrowing against your own labor.
Reserves are not there
A roof with eight years left is an expense accruing right now. Operators carry a per-unit reserve so a capital event is a scheduled cost instead of a crisis. Sellers rarely show one, because it only reduces the number they are selling.
Insurance is last year's premium
This is the fastest-moving line on the statement, and the seller's premium reflects the seller's coverage and history, not the quote you will get at change of ownership. I wrote up what a jump does to a deal in how to underwrite a Tampa Bay rental when insurance premiums jump.
Taxes are at the seller's assessment
In many places a sale triggers a reassessment. Underwriting the seller's tax bill on a building you are about to buy at a higher price is a known error with a knowable answer. Call the assessor.
Capital work is hiding in repairs
A $14,000 roof section booked as maintenance makes the expense line look volatile and the NOI look fine. Capital work belongs in your capital budget, not in NOI, and it belongs in your cash plan either way.
How to rebuild NOI in one sitting
- Get the rent roll and twelve months of statements. Not a summary, not a pro forma. If the seller cannot produce them, that is the finding.
- Replace scheduled rent with collected rent. Work from bank deposits where you can get them.
- Apply your own vacancy and credit loss. Use the market and the building's history, not the current snapshot.
- Price the expenses yourself. Your insurance quote, the assessor's post-sale number, a real management fee, your own repair history on similar buildings.
- Add reserves per unit and move anything capital out of repairs and into your capital plan.
- Stress it. Rents 5% under, vacancy at 10%, expenses up 10%. If the deal only works on the unstressed number, you have a thesis, not a deal.
Loan size follows NOI, so the structure conversation comes after this work, never before. Elite Private Lending arranges fix & flip, bridge and DSCR rental loans on 1 to 10 unit properties through a lending partner. ESCG is not a direct lender, and terms depend on the property and the borrower.
The operator's standard for NOI
A landlord reads the NOI on the broker's sheet. An operator builds it, line by line, from documents, and then watches it every month because it is the number that carries the value of the asset. That distinction is the whole subject of landlord vs. operator.
I operate 125 doors in Tampa Bay, FL and Northeast Pennsylvania, and the rebuild happens on every deal, including the ones from people I trust. It is not suspicion. It is that nobody else is paid to protect that number for you. A finished renovation does not change NOI until the units are leased and collecting, which is the point of when a value-add property is actually stabilized, and in a market where debt is expensive the NOI you can prove is the only basis worth buying on, as in how to buy multifamily when interest rates are high.
Frequently asked questions
What is NOI in real estate?
Net operating income is a property's income after operating expenses and before debt service. You start with the rent and other income you actually collect, subtract vacancy and credit loss, then subtract every cost of running the building, including taxes, insurance, repairs, management, owner-paid utilities and replacement reserves. What remains is NOI, and it describes the building rather than your financing.
Does NOI include the mortgage payment?
No. Debt service is deliberately excluded so that two buyers looking at the same building arrive at the same NOI regardless of how each one would finance it. That is what makes NOI comparable across properties. Your mortgage enters the analysis one step later, in debt service coverage and cash-on-cash return, which describe your position rather than the asset.
How is NOI different from cash flow?
NOI is income before debt service. Cash flow is what is left after you pay the loan. A building can have healthy NOI and almost no cash flow if the debt is expensive or the loan is large. Lenders size loans from NOI, and owners live on cash flow, so an operator tracks both and never substitutes one for the other.
What expenses are left out of NOI?
Mortgage principal and interest, capital improvements such as a roof or new windows, depreciation, your personal income taxes, and loan or closing fees all stay out. Replacement reserves, however, belong in. The common mistake runs the other way: sellers leave out vacancy, management and reserves, which are all real operating costs and all belong in the number.
