Two-income-stream beach property setup. How would you run the numbers on this?

Question

I'm a real estate agent on Fort Myers Beach (disclosing upfront) and I have a listing that I think has a really interesting STR setup, but I want to get some investor perspective on how you'd actually structure and operate it.

The property is a renovated single family home on FMB with a private pool. What makes it unique is a detached lower-level efficiency unit with its own bedroom, bathroom, and kitchenette. Fully air-conditioned, completely separate entrance from the main house. It's non-conforming so it doesn't count in the official square footage, but it functions as a standalone space.

My question for the STR operators here. How would you run this? Would you rent the main house as the primary STR and list the suite separately? Bundle them together as a "whole property" rental and charge a premium for the extra space? Use one for mid-term and one for short-term? Or would you house hack it, live in one and rent the other?

The property is listed at $715K. Mid-island, no HOA, turnkey. I'm curious what kind of revenue projections experienced FMB operators would put on a setup like this, and whether the dual-income angle changes how you'd underwrite the deal compared to a standard single family beach rental.

Appreciate any insight. Happy to share more details about the property if anyone wants to dig into the numbers.

Dominic Mazzarella · Answer

I’d underwrite it a few different ways, but I wouldn’t give the efficiency unit much credit until I knew exactly what’s allowed locally. The private pool and separate unit both sound good on paper, but they can also create extra costs and risk if the city, insurance, or STR rules don’t like the setup. Before getting too excited, I’d want to know whether the efficiency can legally be rented separately, whether the property already has STR history, and what similar homes are actually doing in revenue, not just what AirDNA says.

If it were me, I’d probably run the base case as one whole house STR and then treat the second unit as upside. If the deal only works because the lower unit rents separately, that's a bit risky. If it still comes close as a normal beach rental and the second income stream is bonus upside, that’s a much better position.

Masoud Arouni · Answer

@Justin Jamison the dual income stream is interesting but it complicates the underwriting in ways most investors will not model correctly upfront.

The core challenge is that the two units have fundamentally different risk profiles. The main house as a beach STR is highly seasonal and Airbnb-dependent. The efficiency unit works better as a mid-term rental at 30+ days which gives you more stable income but at a lower nightly rate. Bundling them together as a whole-property rental sounds appealing but you are leaving significant revenue on the table compared to running them separately.

The numbers that matter before anything else at $715K with 25% down and at 7% your monthly mortgage is roughly $3800. Fort Myers Beach STR insurance post-Ian is running $15000-25000 annually on a pool property, let's call it $1700/m. Property taxes will be reassessed at purchase price, so budget another $900/m. You are at $6400/m in fixed costs before management, cleaning, or supplies.

To break even the two units combined need to net $6400/m after Airbnb fees and expenses. At 65% occupancy on the main house at $350/night average that is roughly $6800 gross after fees and cleaning costs you 'd be at $5K net. The efficiency adds $1500-2000/m as a mid-term rental. That gets you to break-even but with very little margin and zero vacancy cushion on the main house.

What is the current insurance quote on the property and what were the actual STR revenues for 2024/25?