How to Underwrite a Short-Term Rental Before You Sign Anything

Most STR investors buy properties wrong. Here is the full underwriting framework: revenue inputs, expense modeling, startup costs, and return metrics that actually matter.

The Most Expensive Mistake in STR Investing Is Falling in Love With the Property

Operators who have been doing this for more than three years have all seen the same pattern. Someone finds a charming cabin in the Smokies or a downtown condo in Nashville. The photos are great. The location feels perfect. They run a quick AirDNA search, see an ADR of $250, and assume 70% occupancy. The math looks incredible. They buy it.

Six months later, the property is running at 48% occupancy because of three competitors who opened in the same period, the cleaning cost is $180 a turn because the nearest cleaning crew is 40 minutes away, and the mortgage payment was calculated using a rate that has since gone up. The deal that looked like a $30,000/year cash flow machine is breaking even at best.

The fix is not complicated. It is building a real underwrite before you make an offer. Here is exactly how to do it.

The 5 Inputs Every STR Underwrite Needs

• 1. Gross revenue projection (conservative, base, and optimistic cases)
• 2. Operating expenses (fixed and variable, fully loaded)
• 3. Startup costs (furniture, photography, supplies, permits)
• 4. Financing costs (mortgage P and I, or lease payment for arbitrage)
• 5. Market demand signals (seasonality, comp supply, regulatory environment)

If your analysis is missing any one of these, you do not have an underwrite. You have a hope document.

Building Your Revenue Projection

Where to Get Reliable Revenue Data

AirDNA Rentalizer is the standard starting point. Enter the address, property type, and bedroom count, and you get an estimated annual revenue, ADR, and occupancy rate based on comparable listings in the area. Treat this as your base case, not your target. AirDNA figures represent market averages, not optimized performance.

For more granular comp research, pull the VRBO pricing calendar on 3-5 direct competitors: same bedroom count, similar location, similar amenities. Check their pricing for the next 60 days and look at how many dates are already booked. This gives you a real-time occupancy signal that AirDNA data (which has a lag) does not.

Seasonality index is critical and often ignored. A property with a 75% annual occupancy average might run at 90% June through August and 45% January through February. If you are buying in a ski market that does most of its revenue in 10 weeks, your cash flow model has to reflect that reality. Seasonal markets need larger operating reserves because the income is lumpy.

Building the Three Scenarios

• Conservative case: Use AirDNA estimates minus 15-20%. Assume your occupancy is lower than the market average for the first 6 months while you build reviews. Use the lower end of the ADR range for your comp set.
• Base case: Use AirDNA estimates at face value. Assume you hit market-average performance within 6 months of launch.
• Optimistic case: Use AirDNA estimates plus 10-15%. Assume you execute better than average on pricing, listing quality, and reviews. This is achievable but requires active management.

Your investment decision should be based on the conservative case making sense. If the deal only works in the optimistic scenario, it is not a deal.

Full Expense Modeling: Where Operators Underestimate

Cleaning Costs

Cleaning is almost always the largest single variable cost, and it is almost always underestimated. Real market rates in 2025:

• 1-bedroom unit: $80 to $150 per turn depending on market and proximity to cleaning crews
• 2-bedroom unit: $100 to $175 per turn
• 3-bedroom unit: $120 to $220 per turn
• Luxury or large properties: $200 to $350 per turn

If you are in a rural market with limited cleaning supply, budget toward the high end and add a buffer. A cleaning labor shortage in peak season is a real operational risk.

Platform Fees

Airbnb charges hosts 3% of the booking subtotal (before cleaning fee) as a host service fee. This sounds small until you model it at scale. On $60,000 in gross annual booking revenue, that is $1,800/year just in Airbnb host fees, before you factor in any guest-side fees that affect your competitive pricing.

VRBO has a different structure: either a subscription model (roughly $499-999/year depending on tier) or a pay-per-booking model at 5-8% of booking value. Model based on which you will use and your expected booking volume.

Supplies and Restocking

Budget $40 to $80 per month per property for consumable supplies (toiletries, paper goods, coffee, cleaning products). New operators typically underestimate this by 50% because they forget that guests go through a remarkable amount of toilet paper, dish soap, and trash bags.

Insurance

STR-specific insurance (not a standard homeowners policy, which typically does not cover STR use) runs $1,200 to $2,500 per year for most residential properties. Factors that push the cost higher: pool, hot tub, wood-burning fireplace, high-value furnishings, and high-crime markets. Do not assume your existing homeowners policy covers STR activity. Most do not.

Software and Tools

• PMS (Hospitable, Hostfully, etc.): $30-100/month depending on number of listings and features

• Dynamic pricing tool (PriceLabs, Wheelhouse, Beyond): $20-50/month per property
• Smart lock subscription (if applicable): $5-15/month per lock
• STR analytics platform: varies

Maintenance Reserve

Budget 1% to 2% of the property value per year as a maintenance reserve. On a $400,000 property, that is $4,000 to $8,000 per year. This sounds like a lot until the HVAC fails in July ($4,000-8,000), the hot tub pump dies ($800-2,000), or the roof needs patching ($1,500-5,000). Maintenance reserves are not optional; they are part of the real cost of ownership.

Utilities

STR utility costs run significantly higher than owner-occupied properties because guests are not paying the bill and have no incentive to be efficient. Estimate $150-300/month for electric in a typical market, higher in extreme heat/cold climates. Budget internet ($60-100/month) and any streaming services you provide separately.

Startup Costs: The Check You Write Before You Make a Dollar

Startup costs are one-time but significant. Get these wrong and your first-year returns look terrible even if operations are strong.

• Furniture and furnishings: $8,000 to $25,000 depending on property size and market. A 1-bedroom in a mid-market needs roughly $8,000-12,000 fully furnished. A 3-bedroom with outdoor seating, quality bedding, and full kitchen setup in a competitive market needs $18,000-25,000.
• Photography: $300 to $600 for a professional STR shoot. Do not skip this. Professional photos measurably improve click-through rates on Airbnb.
• Initial supplies and consumables: $500 to $1,000 to stock the property before the first guest arrives.
• Permit and licensing fees: $50 to $500 depending on jurisdiction, plus potential inspection costs.
• Cleaning before launch: $200 to $400 for a deep clean to get the property guest-ready.

Total startup cost for a 1-bedroom in a mid-market: roughly $10,000-15,000 beyond the property acquisition cost. For a 3-bedroom in a competitive market: $22,000-30,000. Include these in your return calculations.

The Return Metrics That Actually Matter

Break-Even Occupancy

Calculate the occupancy rate you need to cover all fixed and variable costs. If your monthly fixed costs (mortgage, insurance, software, utilities) total $3,200 and your variable cost per booking night is $35 (cleaning allocated per night, supplies), and your average nightly rate is $180, then you need roughly 21-22 occupied nights per month to break even. That is a 70% occupancy rate on a 30-day month. Know this number before you buy.

Cash-on-Cash Return

Cash-on-cash return measures your annual cash flow divided by your total cash invested (down payment plus startup costs plus closing costs). A solid STR cash-on-cash return is 8% to 15%. Below 8% and you would probably do better with a long-term rental. Above 15% and you have found something genuinely good. Deals penciling at 20%+ in today is market exist but require either a great market, excellent execution, or favorable purchase price.

Gross Yield vs Net Yield

Gross yield is annual gross revenue divided by property value. Net yield is annual net cash flow divided by property value. Investors often cite gross yield because it sounds better. Focus on net yield. A property generating $60,000 gross with $52,000 in total expenses has a net yield of $8,000. On a $350,000 property, that is a 2.3% net yield. Not impressive. Know which number you are looking at.

Using the MagicBnB Deal Analyzer

MagicBnB is Deal Analyzer was built specifically for this underwriting process. You input the property details, revenue assumptions, and expense structure, and the tool builds out conservative and optimistic scenarios side by side. Milo, MagicBnBis AI analyst, generates a written analysis of the deal that explains the key risks and assumptions in plain language, the same way an experienced operator would walk through it with you.

The PDF export means you can share the full analysis with a lender, a partner, or an investor without rebuilding the model in a shareable format. The free tier includes 5 deal analyses, which is enough to evaluate a pipeline of properties before committing to anything. Operators who are actively acquiring multiple properties per year use the Pro plan for unlimited analyses.

The difference between the Deal Analyzer and a back-of-napkin AirDNA estimate is the difference between informed confidence and expensive guesswork.

Frequently Asked Questions

How do I calculate if a short-term rental is worth buying?

Build a three-scenario revenue model (conservative, base, optimistic) using AirDNA and VRBO comp data. Model all expenses including cleaning per turn, platform fees, insurance, maintenance reserve, and software costs. Calculate cash-on-cash return (annual net cash flow divided by total cash invested). A target of 8-15% cash-on-cash is a reasonable benchmark for a solid STR investment.

What is a good cash-on-cash return for a short-term rental?

Eight to fifteen percent cash-on-cash return is generally considered solid for STR investing in 2025. Below 8% is marginal compared to alternatives. Above 15% is strong and suggests either excellent market selection, favorable purchase price, or both. Always calculate based on conservative revenue assumptions, not optimistic projections.

How much does it cost to furnish an Airbnb?

Furnishing a 1-bedroom STR for a mid-market typically costs $8,000-12,000. A 3-bedroom in a competitive market runs $18,000-25,000 when fully equipped with quality bedding, outdoor furniture, full kitchen, and the amenities guests expect. Add $500-1,000 for initial supplies and $300-600 for professional photography.

What expenses should I include in a short-term rental underwrite?

Include cleaning labor ($80-220 per turn depending on size), platform fees (3% Airbnb host fee plus factor VRBO fees), supplies ($40-80/month), STR insurance ($1,200-2,500/year), PMS and pricing software ($50-150/month), utilities ($200-400/month), maintenance reserve (1-2% of property value annually), and mortgage or lease payments.

About MagicBnB

MagicBnB is the financial intelligence layer for short-term rental investors and operators. The Deal Analyzer builds conservative and optimistic revenue scenarios with full expense modeling, generates a written AI analysis from Milo, and exports to PDF for sharing with lenders or partners. Once you own properties, the Portfolio Overview Dashboard shows true net profit per property in real time so you can track how performance compares to your original underwrite. Start free at magicbnb.io.