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    Waterfront Duplex with Rental Potential Title is generated by Realmo AI

    330-340 4th Street, Key Colony Beach, FL 33051

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    For Sale
    $1,849,000

    MULTI_FAMILY - Key Colony, FL

    Property size:
    2,540 SF
    Lot size:
    0.15 Acres
    Price / SF:
    $727/SF
    Added:
    Apr 4, 2026
    Days on Market:
    49
    Last Refresh:
    May 22 at 7:06 pm

    Property Features for 330-340 4th Street

    General Information

    Property type
    Residential Multi Family
    Property subtype
    Other
    Zoning
    R-2A - Key Colony Two Fam
    Bedrooms
    3
    Bathrooms
    4
    Rooms
    Bathroom 3, Bathroom 4, Bathroom 2, Bedroom 3, Bathroom 1, Bedroom 1, Bedroom 2
    Parking features
    Open, RV
    Security features
    Security System
    Patio and Porch features
    Patio, Porch
    Pets allowed
    Yes
    Pool private
    1
    Interior features
    Built-in Cabinets, Security System, Storage
    Exterior features
    Fencing, Lighting, Outdoor Shower, Shed, Storage
    Fencing
    Fenced
    Appliances
    Washer, Dryer, Dishwasher, Refrigerator, Range, Oven, Freezer, Ice Machine
    Standard status
    Active
    APN
    00072990-000000
    Size
    2,540 SF
    Lot size
    0.15 Acres

    Taxes and HOA fees

    Tax Year
    2025
    Tax Description
    BK 3 LT 33 KEY COLONY BEACH PB3-120 SHELTER KEY OR380-643 OR455-607 OR687-619 OR1098-2040 OR1098-2046 1098-2047 OR1285-1
    Tax Annual Amount
    10605

    Utilities

    Heating system
    Central
    Cooling system
    Central Air
    Water front
    1

    Building Details

    Year built
    1971
    Flooring type
    Tile, Laminate
    Building materials
    Frame, Hardi Board Siding
    Roof type
    Metal
    Additional Structures
    Storage

    We can help!

    Listing Contact
    Dan Cloud
    Dan Cloud

    Listing agent Dan Cloud License #3144777

    Listing office Water Vista Realty, Inc. 749 Oceana Drive, Key Largo, FL

    Listing date Apr 4, 2026

    MLS# 619361 Listing URL

    Copyright © 2026 Florida Keys Board of REALTORS®. All rights reserved. All information provided by the listing agent/broker is deemed reliable but is not guaranteed and should be independently verified.

    HighLights

    • Waterfront duplex with deep water dockage (60 ft), new 15K lbs boat lift (2022), and extra‑wide canal.
    • Excellent rental income opportunity with 7‑day rentals allowed.
    • New (2022) heated and chilled saltwater pool with cool deck.
    • Located in Key Colony Beach, a NO HOA municipality, with access to amenities.
    • Extensive upgrades including a new roof (2013), hurricane shutters (2021), upgraded electrical system (2022), mini‑split AC (2021), flooring, doors, and windows.
    • Ample parking space for 12 cars, 2 RVs, and 2 boats/trailers, along with ample storage space.

    Overview

    This renovated waterfront duplex, located in Key Colony Beach, offers an excellent rental income opportunity with 7-day rentals allowed. The property features a 2-bedroom, 2-bathroom upper level and a 1-bedroom, 1.5-bathroom lower level, both equipped with full kitchens. A new 15,000 lbs. boat lift was installed in 2022, along with a 60 ft deep water dock, an extra-wide canal, multiple electrical outlets, and three fresh water spigots. The house is equipped with surge protection and a transfer switch for a portable generator. Exterior motion lights are equipped with security cameras. The property includes a new heated and chilled pool with a saltwater system installed in 2022, along with a new Pool-Cool Deck concrete patio. An outdoor shower is also present. The metal roof was installed in 2013, and hurricane accordion and metal Bahama shutters were added in 2021. The electrical system was upgraded in 2022, along with upgraded flooring, doors, and windows. A mini-split AC unit was installed in 2021. The upper level features a covered balcony with views of the pool and boat dock. Ample storage is available in three large outdoor access rooms and a shed. The property offers parking for 12 cars, 2 RVs, and storage for 2 boats or trailers. Located on the ocean side, it is minutes from fishing and diving spots such as the Gulfstream, Coffins Patch Reef, and Sombrero Reef Lighthouse, with easy Bayside access via Vaca Cut. Key Colony Beach amenities include a 9-hole par 3 golf course, tennis and pickleball courts, basketball, bocce ball, corn hole, and horseshoes, as well as parks, playgrounds, and walking and bike pathways. The property is located in a no-HOA municipality on Marathon Island MM53, with a lot size of 0.15 acres and a property size of 2540 square feet.
    Property Profile Location Intelligence

    Current Use by Public Records

    Duplexes

    Map

    City
    Key Colony Beach
    County
    Monroe
    State
    Florida
    Longitude
    -81.0216
    Latitude
    24.7226

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    FAQs

    What type of property is this?
    Duplex - Renovated waterfront duplex in Key Colony Beach with rental income.
    Where is this duplex located?
    The property is located at 330-340 4th Street Key Colony Beach, FL.
    What is the asking price?
    The asking price for this property is $1,849,000.
    What are key features of this property?
    This property features: Waterfront duplex with **deep water dockage (60 ft)**, new **15K lbs boat lift (2022)**, and extra‑wide canal.; Excellent rental income opportunity with 7‑day rentals allowed.; New (2022) **heated and chilled saltwater pool** with cool deck.
    (305) 396-7844
    We can help!
    Listing Contact
    Dan Cloud
    Dan Cloud
    Real Estate License ID: 3144777
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    Realmo Value Estimations

    Realmo estimates a property’s market value using a proprietary methodology that incorporates public data and user-submitted information. This cumulative value is generated by integrating a variety of conventional and innovative methods. 

    Disclaimer

    These figures are not official appraisals and should not be used as a substitute for a valuation performed by a licensed appraiser.
    Actual market value may differ due to factors not captured in the data. Estimates are offered for informational purposes only, and users should conduct independent research before making financial or investment decisions.
    By using this feature, you acknowledge that Realmo is not responsible for actions taken based on these estimates.

    AI approach

    Realmo AI Method estimates property value using machine learning models trained on millions of comparable listings, transactions, and market signals. It analyzes property features, location intelligence data, and current market dynamics to predict the most probable market value in real time.

    Realmo CapRate Calculation

    Realmo calculates the Capitalization Rate (Cap Rate) to help estimate a property's potential return on investment. The Cap Rate is a fundamental metric in commercial real estate that measures the relationship between a property's net operating income and its market value.

    How We Calculate Cap Rate

    Cap Rate Formula:
    Cap Rate (%) = (Net Operating Income / Property Value) × 100

    Net Operating Income (NOI) Formula:
    NOI = Area × Lease Rate × (1 - Vacancy Rate) × (1 - Operating Expense Ratio)

    Components

    Net Operating Income (NOI) represents the annual income a property generates after operating expenses:

    • Area: Building square footage from property records
    • Lease Rate: Annual $/sqft based on market data for the property type and geographic location
    • Vacancy Rate: Percentage of unoccupied space based on market data for the property type and location
    • Operating Expense Ratio: Operating costs as a percentage of income, varies by property type

    Property Value is derived from:

    • Recent sale price (if available)
    • Statistical models using comparable sales
    • AI-powered valuation estimates

    Example Calculation

    For a 100,000 sqft Office Building:

    • Lease Rate: $25.00/sqft/year (market data for Office in this area)
    • Vacancy Rate: 8% (market data for Office in this area)
    • Operating Expense Ratio: 35% (typical for Office properties)
    • Property Value: $15,000,000

    Step 1: Calculate NOI

    NOI = 100,000 × $25.00 × (1 - 0.08) × (1 - 0.35)
    NOI = 100,000 × $25.00 × 0.92 × 0.65
    NOI = $1,495,000/year

    Step 2: Calculate Cap Rate

    Cap Rate = ($1,495,000 / $15,000,000) × 100
    Cap Rate = 9.97%

    Property Type Considerations

    Net Operating Income calculations vary by property type due to different operating expense ratios:

    • Office: Higher expenses (30-40%) for HVAC, utilities, maintenance
    • Retail: Moderate expenses (25-35%) for common area maintenance
    • Industrial/Warehouse: Lower expenses (15-25%) for minimal tenant services
    • Multifamily: Moderate expenses (35-45%) including property management
    • Self-Storage: Lower expenses (25-35%) due to minimal maintenance

    Market lease rates and vacancy rates are specific to each property type and geographic location, reflecting local market conditions.

    Disclaimer

    These calculations are estimates for informational purposes only and should not be used as a substitute for professional financial analysis or appraisal.

    • Cap Rate calculations depend on market data that may change over time
    • Actual operating expenses, lease rates, and vacancy rates may differ from market averages
    • Individual property conditions, lease terms, and tenant quality significantly impact actual NOI
    • Property value estimates are approximations and not official appraisals
    • Cap rates vary widely by market, property condition, and investment risk profile

    Professional Guidance Recommended: Before making any investment or financial decisions, consult with licensed appraisers, commercial real estate brokers, and financial advisors who can evaluate your specific property and circumstances.
    By using this feature, you acknowledge that Realmo is not responsible for investment decisions or actions taken based on these estimates.

    Cap approach

    Capitalization Method calculates value based on estimated net operating income (NOI) and applying a market-based capitalization rate (cap rate), we estimate what a typical investor might be willing to pay for it.

    Comparable approach

    Comparable estimate is based on recent sales of similar nearby properties, adjusted for factors like size, condition, and location.

    Relative

    Relative property class coefficient uses factors that account for typical price differences between various asset types (e.g., retail vs. industrial) to provide a more accurate market-aligned estimate.

    Geo

    Comparable Sales Method, enhanced by Geo coefficients — location-based adjustment factors that reflect differences in price levels across neighborhoods, cities, or regions ensuring a more accurate, market-sensitive valuation.

    Stat Estimate

    This method estimates value based on actual market adjusted recent (~5 years) sales of comparable properties around by location and property type.

    • Ranges - area data calculated by industry standard IQR Outlier Removal Method
    • Range-from: 75% of all similar sales ($/sqft) are above this value
    • Range-to: 75% of all similar sales ($/sqft) are below this value
    AI Estimate

    This method estimates value based on AI market estimation of comparable properties around by location and property type.

    • Ranges - area data calculated by industry standard IQR Outlier Removal Method
    • Range-from: 75% of all estimations ($/sqft) are above this value
    • Range-to: 75% of all estimations ($/sqft) are below this value
    Alternative use

    Estimate considers the property’s potential value if used for a different purpose-based on zoning, demand, and market feasibility.

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