The brokers who win listings are the ones who can sit across from an owner and, in 15 minutes, tell them what their building is worth, how it would trade today, and what a sophisticated buyer would underwrite. You don't need ARGUS for this. You need a repeatable napkin-math framework. Here it is.
Step one: establish income. Ask for the rent roll, or build a synthetic one from market rents. Multiply rentable square footage by gross rent per square foot to get potential gross income. For a 25,000 sq ft flex building at $14 NNN, that's $350,000. If the building is partially vacant or has below-market leases, note it — that's value-add upside you'll come back to.
Step two: subtract a vacancy factor. Use 5% for stabilized multi-tenant, 7–10% for older or tertiary-market product, and zero only for single-tenant credit deals. From our example: $350,000 minus 7% = $325,500 effective gross income.
Step three: subtract operating expenses. On a true NNN lease, the landlord's OpEx is minimal — reserves, management, and non-reimbursables — usually $1.00 to $1.50 per square foot. On a gross or modified-gross lease, expenses run $4 to $8 per square foot depending on age and asset class. For our flex building NNN, assume $1.25 per foot, or $31,250. Net operating income = $325,500 minus $31,250 = $294,250.
Step four: apply a cap rate. This is where local knowledge separates pros from amateurs. Don't guess — anchor to two or three recent sales in the same submarket, same product type, same vintage. If recent flex comps traded at 7.5%, your value is NOI divided by cap rate: $294,250 ÷ 0.075 = $3,923,000, or about $157 per square foot. Round to $3.9M and you have a defensible opinion of value in under five minutes of math.
Step five: sanity-check with two other lenses. Price per square foot — does $157 line up with replacement cost and recent comps? Gross rent multiplier — does the price divided by gross rent (about 11x here) match the submarket? If your three methods agree within 10%, you have a strong number. If they diverge, dig into why before you quote anything.
Step six: layer in financing to test buyer demand. At 65% LTV and a 7.25% interest rate on a 25-year amortization, the debt service on $2.55M of debt is roughly $220,000 annually. That leaves $74,250 of cash flow on $1.37M of equity — a 5.4% cash-on-cash return. Ask yourself: would a buyer in today's market accept a 5.4% return on this asset class? If yes, your price is realistic. If no, your cap rate is too low or your expenses are too light.
Step seven: identify the value-add story. Is one tenant paying $11 when the market is $14? That's $75,000 a year of upside on rollover, worth roughly $1M at a 7.5% cap. Is the building 80% leased with one 5,000 sq ft vacancy? Lease it up and you've created $400,000 of value. The best brokers don't just price the building as-is — they show the owner the gap between today's value and stabilized value, which is exactly the conversation that wins listings.
A few rules to keep you honest. Never use pro-forma rents in your going-in number — sophisticated buyers won't. Always reconcile your cap rate to actual closed comps, not to listing cap rates which are aspirational. And always state your assumptions out loud when you present a number — 'at $1.25 of OpEx, a 7.5% cap, and 7% vacancy, we're at $3.9M' — because the owner who challenges your assumptions is the owner who's about to hire you.
Do this 20 times on real buildings in your farm and the math becomes automatic. Then you can stop talking about being a market expert and start sounding like one in every conversation.
