I was underwriting a short-term rental in Scottsdale. I'd already run the revenue comps. The numbers looked strong. I plugged in my cleaning costs at $150 per turnover, the same rate I'd been paying in Chicago, and the cash flow projections looked great.

There was one problem: cleaning in Scottsdale costs $250 per turnover. That single miscalculation created an $8,000 annual gap. On a property projecting $20,000 in cash flow, I'd lost 40% of my profits before I even started.

The Expenses Problem Nobody Talks About

Every STR investor loves talking about revenue. Revenue comps, revenue forecasts, revenue potential. And revenue matters. But it's only half the equation.

Your operating expenses determine whether a high-revenue property actually puts money in your pocket or quietly bleeds you dry. And the most common underwriting mistake isn't bad math. It's lazy inputs.

The Expenses That Trip People Up

Cleaning costs are the most common offender. Labor rates vary dramatically by market. A four-bedroom clean in a low-cost-of-living city might run $150. The same clean in a resort market could be $250-$300. That difference, multiplied by 50-80 turnovers per year, is five figures.

Utilities are the second trap. A property with a heated pool, a hot tub, and four-zone HVAC in Phoenix will have a very different electric bill than a three-bedroom cabin in the Smoky Mountains.

Property management fees are percentage-based, which means they scale with your revenue in the wrong direction. At 15%, a property generating $120,000 in revenue costs you $18,000 in management fees.

Get every expense line right. STRProfitMap's Property Analyzer breaks down operating costs so nothing gets missed.

The Fix Takes Three Phone Calls

For cleaning costs: call three cleaning companies in your target market. Get quotes for your specific property size and turnover frequency. Use the average.

For utilities: call a local property management company. Ask what electricity, water, gas, and internet cost for a property like the one you're considering. They know. They manage dozens of similar properties.

Property taxes are public record. Check Zillow or the county assessor's website. Insurance requires an actual quote from an agent, not a number borrowed from a Reddit thread about a different state.

Setup Costs Are Equally Dangerous

A hot tub costs $7,500 at the store. But once you add the electrician ($500-$1,500), the concrete pad ($1,000-$3,000), delivery and placement ($200-$500), and any required permits, you're closer to $10,000-$12,000.

The investors who underestimate setup costs end up in a bind: they've committed to a property based on revenue projections that require certain amenities, but they've run out of budget to install those amenities.

Reunderwrite When Reality Changes

During the inspection period you discover the roof needs replacing. That's $15,000. A contractor tells you the electrical panel can't support a hot tub without an upgrade. Another $3,000.

When new costs surface, plug them back into the sheet. Don't rationalize them away. The spreadsheet doesn't care about your feelings. It cares about inputs. Give it honest ones and it tells you the truth.

Start with reliable market data. STRProfitMap filters to proven listings so your revenue estimates are grounded in reality, not inflated averages.

Build Your STR Analysis on Numbers You Can Defend at STRProfitMap. Because the deal that looks great on a spreadsheet full of guesses is the deal that burns you.