To evaluate a commercial real estate investment, start with the income the property produces, then test it against price, financing, tenant risk and the physical condition of the building. In practice that means calculating net operating income (NOI), converting it to a cap rate and cash-on-cash return, reviewing the rent roll and leases, inspecting the property, and stress-testing the numbers with conservative assumptions before you make an offer.
Step 1: Understand how the property makes money
Commercial property is valued mainly on the income it generates, not on what comparable buildings "feel" like they are worth. Before running any formula, write down in plain words where the income comes from: how many tenants, what type of leases, when those leases expire, and who pays the operating costs. A fully leased building with one long-term tenant behaves very differently from a multi-tenant building with several short leases, even if both show the same income today.
Property type matters too. Retail centers, flex and warehouse buildings, office buildings and land each carry different risks. Our overview of six types of commercial real estate investments is a good place to compare them before you narrow your search.
Step 2: Calculate net operating income (NOI)
NOI is the property's annual income after operating expenses but before loan payments, income taxes and depreciation. The basic formula is effective gross income minus operating expenses. Effective gross income means scheduled rent plus other income, less an allowance for vacancy and unpaid rent. Operating expenses include real estate taxes, insurance, utilities, maintenance, management and, where the owner pays them, common area costs.
Hypothetical example: a small building has $300,000 in scheduled rent, a 5% vacancy and collection allowance ($15,000), and $90,000 in operating expenses the owner cannot pass on. NOI is $300,000 − $15,000 − $90,000 = $195,000. We walk through each line item in how to calculate NOI for a commercial property.
Step 3: Convert NOI into a cap rate and a value
The capitalization rate (cap rate) equals NOI divided by price. It lets you compare the income yield of different properties on an unleveraged basis. In the hypothetical example above, a $2,600,000 price produces a cap rate of $195,000 ÷ $2,600,000 = 7.5%. Cap rate also works in reverse: NOI divided by a cap rate gives an indicated value.
Be careful with any cap rate quoted to you. The question is always which NOI it is based on: the seller's current numbers, or numbers you have verified. For help interpreting the figure, read what is a good cap rate for commercial real estate. Current market cap rates vary by property type, location, tenant quality and lease length, so confirm them with recent comparable sales from a source such as CoStar or a broker's analysis rather than relying on a rule of thumb.
Step 4: Analyze the rent roll and the leases
The rent roll lists every tenant, suite size, rent, lease dates, and deposits. Check it against the actual leases, because rent rolls prepared by sellers can contain errors or omit side agreements. Look for:
- Lease expirations: a large share of income expiring in the same year is a rollover risk.
- Rent versus market: below-market leases may offer upside; above-market leases may reset lower.
- Expense structure: whether leases are NNN, modified gross or full service determines how much of the operating cost the owner really carries. See what a triple net lease is.
- Tenant concentration: one tenant paying most of the rent concentrates your risk.
- Options and rights: renewal options, termination rights, purchase options and exclusives can change the value.
Our guide to analyzing a commercial property rent roll covers this step in more detail.
Step 5: Measure return with financing in the picture
Cap rate ignores debt. Most buyers also want to know their cash-on-cash return, which is annual pre-tax cash flow divided by the cash invested. Continuing the hypothetical example, suppose NOI is $195,000, annual loan payments are $140,000, and the buyer invests $900,000 in cash (down payment plus closing costs and reserves). Cash flow after debt service is $55,000, and cash-on-cash return is $55,000 ÷ $900,000, about 6.1%.
Also calculate the debt service coverage ratio (DSCR), which is NOI divided by annual debt service. In the example, $195,000 ÷ $140,000 is about 1.39. Lenders set their own minimum DSCR requirements, and they differ, so ask your lender early. A deal that works only with aggressive loan terms leaves little room for error.
Step 6: Review the property itself
Numbers on a spreadsheet do not show a failing roof or an undersized parking field. Plan on these checks during your due diligence period:
- Physical inspection of the roof, HVAC, parking surface, structure and building systems.
- Environmental review, which lenders commonly require. Ask your attorney and lender what they need for your property type.
- Zoning and permitted use, confirmed with the local jurisdiction. In Northern Virginia, rules differ among Fairfax, Loudoun and Prince William counties and the towns and cities within them.
- Title and survey review, including easements and access.
- Estoppel certificates from tenants confirming the lease terms and that no disputes exist.
- Capital needs: a realistic budget for repairs, tenant improvements and leasing commissions you will owe when spaces turn over.
Step 7: Consider location and demand drivers
Location in commercial real estate is about the specific use. For industrial and flex space, access to I-95, Route 1, I-66 and Route 28 affects tenant demand. For retail, visibility, traffic counts and the surrounding rooftops matter. For office, proximity to Metro, Tysons, Reston or the Dulles corridor and the quality of the building shape leasing. Near Ashburn, the Loudoun data center cluster has influenced demand for land and power-ready sites. Ask a broker for current submarket data instead of assuming any trend will continue.
Step 8: Stress-test your assumptions
Re-run your numbers with conservative inputs. What happens to NOI if the largest tenant leaves? If vacancy doubles? If real estate taxes are reassessed after the sale? If your loan rate resets higher? Use a table like this to keep scenarios side by side (all figures hypothetical):
| Scenario | NOI | Annual debt service | DSCR |
|---|---|---|---|
| Base case | $195,000 | $140,000 | 1.39 |
| Vacancy doubles (extra $15,000 lost) | $180,000 | $140,000 | 1.29 |
| Largest tenant leaves ($60,000 rent lost) | $135,000 | $140,000 | 0.96 |
The last row shows why tenant concentration matters: the property would no longer cover its loan payments from operations alone.
Step 9: Check the price against comparables
Compare the asking price with recent sales of similar properties on price per square foot, cap rate and income. Adjust for age, condition, lease terms and location. An appraisal, a broker opinion of value and a CoStar comparables search each give a different angle. Our article on determining the market value of a commercial property explains these methods.
Common mistakes to avoid
- Relying on the seller's pro forma instead of actual operating statements.
- Leaving out management fees, reserves or leasing costs from expenses.
- Buying on cap rate alone without checking lease length and tenant strength.
- Skipping tenant estoppels or the review of the actual leases.
- Underestimating closing costs, loan fees and the time it takes to lease vacant space.
This article is general education, not legal, tax or investment advice. Consult an attorney and a CPA before you buy.
Next step
If you are weighing an acquisition in Northern Virginia, we can help you screen opportunities, run the numbers and request the right documents. Call us at 703-505-3501 or contact us online. You can also browse our investment opportunities, and current properties for sale. Our acquisition overview outlines the buying process from offer to closing.
Frequently asked questions
What is the most important number when evaluating a commercial property?
Net operating income is the foundation, because value, cap rate and loan sizing all flow from it. But NOI is only as reliable as its inputs, so verify income and expenses against leases, bank statements and tax bills.
How do I know if the asking price is fair?
Compare it with recent sales of similar properties and with the income-based value from NOI and a supportable cap rate. An appraisal or a broker's analysis using sales data from a source such as CoStar can confirm it.
What is the difference between cap rate and cash-on-cash return?
Cap rate is NOI divided by price and ignores financing. Cash-on-cash return is annual cash flow after debt service divided by the cash you invested, so it reflects your loan.
What is DSCR and why do lenders care?
Debt service coverage ratio is NOI divided by annual loan payments. It shows whether the property's income can cover the debt. Minimums vary by lender and property type.
What documents should I ask the seller for?
Typically the rent roll, leases and amendments, two to three years of operating statements, tax bills, insurance details, service contracts, and any property condition or environmental reports. Your broker and attorney can tailor the list.
How long is due diligence?
It is set by the purchase contract and negotiated deal by deal. Allow enough time for inspections, lease review, financing and tenant estoppels, and have your attorney review the contract terms.
Should a first-time investor use a broker?
A broker can help find opportunities, analyze comparables and coordinate the process, but you should still involve an attorney, a CPA and a lender. The broker's role is not a substitute for those advisors.
