AirDNA Projected $120K. The Property Needed $340K Cash to Close. Here's How We Build a Real Pro Forma Before You're Under Contract

AirDNA is not a pro forma. It is a market snapshot. Investors who treat it like a financial model are the ones who call us six months after closing, wondering why their numbers don't match reality.

We have closed over $40M in STR transactions in the past year, with 141% year-over-year growth and $70M in total volume. We have run hundreds of pro formas on Nashville short-term rentals. The gap between what AirDNA shows and what a property actually nets is rarely small, and it is never in your favor.

Here is how we build a real pro forma before you are ever under contract.

Why AirDNA Is a Starting Point, Not a Conclusion

AirDNA aggregates revenue data from comparable listings in a given market. It does not have access to the specific property's historical performance. It does not know what your property rents for, how it is managed, or how it has been reviewed.

What it gives you is a market-level estimate based on comps. That comp pool includes professionally managed properties with strong review histories, boutique operators who have been in the market for five years, and brand-new listings that have not yet ranked. All of that gets averaged together and presented as your projected revenue.

In Greater Nashville right now, we are seeing AirDNA revenue estimates run 20 to 35 percent above what first-year operators actually net. That gap comes from three places: ramp-up periods, seasonality cliffs, and 2026 market normalization.

A new listing in East Nashville or The Nations does not earn market-rate ADR on day one. It earns it after 60 to 90 reviews and six months of algorithm positioning. AirDNA does not model that.

Nashville's STR market also has hard seasonality. Q4 and January are soft. If you close in October and your pro forma assumes full-year market comps, you are underestimating the drag of your first winter by a significant margin.

And the broader market: new construction STRs are adding inventory across permit zones faster than demand is absorbing it. The 2024 numbers that AirDNA is drawing from are not the 2026 numbers you are buying into.

"AirDNA tells you what a market earns. A real pro forma tells you what this property earns. They are not the same number." - Jack Costigan

The Expense Stack AirDNA Doesn't Touch

AirDNA projects gross revenue. It does not model a single dollar of expenses. That is not a criticism of the tool. It is just what it is. The problem is investors who stop there.

Here is the expense stack we apply to every Nashville STR pro forma:

Property management fees: 20 to 30 percent of gross revenue. If you are self-managing, this number is zero on paper and enormous in time. Most investors in our client base are physicians, business owners, or executives. Their time has real cost. We use 25 percent as the baseline for full-service management.

OTA platform fees: Airbnb and VRBO both charge the host approximately 3 percent of the booking total. Not optional. Not negotiable. Comes right off the top.

Cleaning costs per turn: Varies by property size, but in Nashville you are looking at $150 to $350 per clean depending on the home. A four-bedroom property averaging 15 turns per month at $250 per clean is $3,750 per month before anything else.

Maintenance reserve: We model 5 to 8 percent of gross revenue. STR properties turn over faster than long-term rentals. Appliances, HVAC, hot tubs, outdoor furniture, smart locks, and TVs all have shorter replacement cycles under high-occupancy short-term use.

Property taxes, insurance, utilities: These are fixed and non-negotiable. STR-specific insurance in Tennessee runs $3,000 to $6,000 annually depending on the property. Utilities for a guest-occupied property run higher than owner-occupied. None of this appears in an AirDNA projection.

Mortgage at current rates: A $500K STR purchase at 25 percent down with an investment property rate around 7.5 percent means a monthly principal and interest payment of approximately $2,625. That is $31,500 per year in debt service alone.

When you layer all of this onto a gross revenue projection, the net number looks very different.

The Cash-to-Close Reality Nobody Advertises

Here is what it actually takes to close on a $500K STR in Nashville right now.

25 percent down: $125,000. Closing costs at approximately 2 to 3 percent: $10,000 to $15,000. Furniture, photography, smart home setup, initial supplies: $30,000 to $40,000 depending on the property.

Total cash required before you earn a single dollar: $165,000 to $180,000.

That is not a criticism of the investment. It is the reality of the asset class. Investors who plan for it execute well. Investors who only modeled the down payment get surprised at the closing table or, worse, launch a property that is under-furnished and under-positioned because they ran out of capital.

The setup budget is not optional. A poorly photographed, under-furnished STR in a permit-zoned Nashville corridor will rank below comparable properties and earn below-market rates for months. The cost of cutting corners on setup compounds.

How We Actually Build the Pro Forma

Our process has four steps.

First, we pull AirDNA for the market and sub-market. East Nashville, The Gulch, and The Nations each have distinct occupancy profiles, ADR ceilings, and demand drivers. We want to understand the market-level range before we touch property-specific data.

Second, we request trailing 12-month actuals from the seller. Not their projection. Their booking history, occupancy rates, and gross revenue by month for the past year. If a seller cannot or will not provide this, that is information.

Third, we cross-reference those actuals against comp actuals, not AirDNA estimates. We have relationships with operators across Nashville who share performance data. We know what comparable properties in the same permit zone actually netted last year.

Fourth, we build three scenarios: conservative, base, and optimistic. The conservative scenario models a ramp-up period, below-market occupancy for the first 90 days, and a 10 percent haircut on ADR relative to comps. The base scenario models mature-property performance at market occupancy. The optimistic scenario models top-quartile occupancy and ADR, fully optimized.

Most sellers present the optimistic scenario. Most buyers only read the optimistic scenario. We present all three and make a buy decision based on the conservative one.

"If the deal only works at the optimistic number, it is not a deal. It is a bet." - Jack Costigan

What Happened on the $120K AirDNA Property

A client brought us a Nashville STR with an AirDNA projection of $120,000 annually. Strong permit zone, good location, well-photographed listing. On paper, it looked like a strong yield at the asking price.

We ran the full pro forma.

Gross revenue, modeled conservatively with a ramp-up period and realistic seasonality: $72,000. Net after management fees, OTA fees, cleaning, maintenance reserve, insurance, utilities, and debt service: $43,000.

Still a serviceable return. But not at asking price.

We went back to the seller with the actual numbers. Not an opinion. A documented pro forma with line-item expense modeling. The seller negotiated down $28,000.

At the adjusted purchase price, the deal made sense. At the original asking price, the investor would have been underwater in year one and wondering why their AirDNA projection never materialized.

That $28,000 negotiation paid for our fee many times over. It came entirely from doing the work that most buyers skip.

Nashville-Specific Considerations in 2026

The Nashville STR permit landscape matters. Not every property in every neighborhood qualifies for an STR permit, and permit status is not always disclosed cleanly in listing materials. We verify permit eligibility and current permit status before any client makes an offer.

New construction STRs in the Gulch and surrounding corridors are adding inventory at a pace that is applying downward pressure on ADR. If you are underwriting based on 2023 or 2024 comp performance in high-construction corridors, you are buying yesterday's numbers.

East Nashville continues to perform well on occupancy, but ADR growth has plateaued. The Nations and Sylvan Park are showing strong demand from bachelorette and group travel. These micro-market distinctions matter at the pro forma level.

[Internal link: Learn more about our STR advisory process and how The Costigan Group structures investments across Nashville's permit zones.]

Frequently Asked Questions

Is AirDNA completely unreliable? No. It is a useful tool for understanding market-level revenue ranges. The problem is using it as the only data source for a purchase decision. We use it as the first input in a multi-step process, not the conclusion.

How do I get trailing 12-month actuals from a seller? Request them directly as part of your due diligence. A motivated seller with strong performance will provide this. Hesitation or unavailability of this data is a signal worth taking seriously.

What occupancy rate should I model for a new Nashville STR? We model 55 to 65 percent in the first 90 days and 68 to 75 percent at maturity for well-positioned Nashville properties. Top-quartile operators in strong locations can exceed 80 percent, but that should be your upside scenario, not your base case.

How much does STR-specific insurance actually cost in Tennessee? Budget $3,000 to $6,000 annually for a single-family STR depending on property size and coverage limits. Standard homeowner's policies do not cover commercial short-term rental activity.

Do management fees vary much between companies? Yes. Discount operators charge 15 to 18 percent but often provide minimal active management. Full-service operators with dynamic pricing, professional photography, and guest relations run 25 to 30 percent. The cheaper option is not always cheaper when you factor in occupancy and ADR performance.

What is the biggest mistake STR investors make in Nashville right now? Skipping the trailing actuals request and building the entire underwrite on AirDNA comps. The second-biggest mistake is underestimating setup costs and launching a property that cannot compete visually in a market where guests have 50 comparable options.

How does the 2026 STR market in Nashville compare to 2023 or 2024? More competitive. More inventory from new construction. More permit enforcement in historically permissive zones. Investors who bought in 2021 or 2022 at lower purchase prices and lower interest rates have different economics than buyers entering now. You are not buying their deal. You are buying 2026 math.

The Investors Who Win Build the Pro Forma

AirDNA is a tool. A pro forma is a discipline.

The investors who get hurt bought the projection. The ones who win built the pro forma, ran the conservative scenario, requested the actuals, and either got the price adjusted or walked away.

We have done this across $70M in closed volume. The math is consistent: properties that are underwritten with real expense modeling at conservative revenue assumptions perform well over time. Properties bought on optimistic projections with no expense modeling disappoint within 12 months.

The work is not complicated. It is just thorough. And thorough is what we do.