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Waterfront · Single Family Residence
$19,900,000$6,451 / sqft
520 S Mashta Dr, Key Biscayne FL 33149
Listed
5
Bedrooms
4
Bathrooms
3,085 sqft
Interior
1961
Year built
None
HOA
Single Family Residence
Type
About this home
Seize a rare opportunity to create a landmark waterfront estate on one of the largest residential lots in Key Biscayne’s exclusive Mashta Island enclave. Spanning an extraordinary 22,140 square feet, this exceptional property offers 138 feet of pristine water frontage and sweeping open water views, providing an unparalleled setting for a world class residence. Plans by renowned architect, Pablo Corazzini of Vitalini Corazzini Architects, are available to the buyer, offering a thoughtfully conceived vision that takes full advantage of the property’s remarkable scale, premier waterfront setting, and spectacular sunsets. The proposed design creates an extraordinary canvas for sophisticated indoor-outdoor living and entertaining, should the buyer choose to pursue the concept. With its exceptional lot size, expansive water frontage, and coveted Mashta Island address, this is a truly irreplaceable opportunity to create a legacy estate in one of South Florida’s most prestigious waterfront communities.
Features
- First Floor Entry
- Split Bedroom
- Family Room
- Bay
- Direct Ocean
Leasing
- Minimum lease
- Not stated
- Ok To Lease
Leasing terms as stated in the MLS listing, not verified by us. The association’s governing documents control what is actually permitted and can change — confirm before you buy.
Location
Run the numbers
We fill in the price and the building's HOA dues. That leaves tax, insurance and maintenance — they depend on your exemptions, your insurer and the unit, so we don't guess them. Rent starts from what comparable units are asking nearby. Vacancy and the loan terms below start at common defaults; change them.
Median asking rent for 5-bed rentals in Key Biscayne, from 9 active listings; the middle half ask $22,000–$40,000.That is what landlords ask, not what units let for — edit it if you know better.
Our default, not a market figure
From the listing
Depends on assessed value & exemptions
Varies widely by building
Repairs, turnover, management
Cap rate
Cash-on-cash
Monthly cash flow
Net operating income
Enter property tax, insurance, maintenance to see the returns. A cap rate calculated without every cost overstates the deal — often by half — so we don't show a partial one.
Illustration only — not a loan offer, quote, or investment advice. We are not a lender and neither offer nor arrange financing. The loan fields start at 20% down over 30 years at 6.5% (rates as of July 2026); that is a nominal rate for illustration, not an APR, and your actual terms will differ. Cap rate is unlevered; cash-on-cash counts the down payment as invested capital and excludes closing costs.
Listing data from the MIAMI Association of REALTORS® (MIAMIRE) IDX program. Information deemed reliable but not guaranteed. Demo data shown for layout purposes.