544 Warren Ln
Key Biscayne, FL 33149 · single_family · For Sale · 4 days on market
Asking price$8,000,000
6 beds 6 baths 1,044 sqft
Suggested offer$1,640,187$6,359,813 above the est. market value of $1,640,187.
View on Realtor.com →Listed by James Duncan · Duncan Studio Real Estate Division Pllc
Typesingle_family
Built2026
Price / sqft$7663
Est. value (own analysis)$1,640,187
Rent estimate (own analysis)$27,000/mo
HOANone
1 / 60
Show every detail
Statusfor_sale
Listed date2026-08-29
Removed date—
MLSMiamiMLS #A12079811
Coordinates25.69138, -80.16925
Address544 Warren Ln
CityKey Biscayne
StateFL
Zip33149
Listing ID6237879602
Sourceus-real-estate-listings, cached 2026-08-31
ZIP market snapshot (33149)
Typical home value (ZHVI)$1,692,135
Typical rent (ZORI)$7,910/mo
Zillow Research's ZHVI (home value index) and ZORI (rent index) for this ZIP, as of 2026-07 — free published data, refreshed monthly, no RentCast quota spent. "Typical value/rent" is a smoothed index, not a literal median of active listings.
Underwriting (buy-and-hold, default assumptions)
| Acquisition (one-time, not monthly/yearly) | |
| Purchase price | $8,000,000 |
| Down payment (20.0%) | $1,600,000 |
| Loan amount | $6,400,000 |
| Closing costs (5.0%) | $400,000 |
| Total cash to close | $2,000,000 |
| Income | |
| Rent (comp-derived) | $27,000$324,000 |
| Vacancy loss (8.0%) | |
| Effective gross income | $24,840$298,080 |
| Operating expenses | |
| Property tax (placeholder 1.9% of price) | $12,667$152,000 |
| Insurance (placeholder 0.8% of price) | $5,333$64,000 |
| HOA dues | $0$0 |
| Management (0.0% of EGI) | $0$0 |
| Maintenance (5.0% of GSR) | $1,350$16,200 |
| Total operating expenses | $19,350$232,200 |
| Net operating income (NOI) | |
| Debt service & reserves | |
| Debt service (6.66%, avg 30yr rate as of 2026-08-27, 30yr amortizing) | |
| CapEx reserve (5.0% of GSR) | $1,350$16,200 |
| Mortgage insurance (PMI) (0.0% of loan, not required — down payment ≥ 20%) | $0$0 |
| Cash flow |
Cap rate
Cash-on-cash
DSCR
Rent-to-price (1% rule)
Gross rent multiplier
Operating expense ratio
Break-even occupancy
Comparables
Same ZIP. Real active rental listings, used to derive the rent estimate above.
| Address | Type | Beds | Baths | Sqft | Asking rent | Listed | Days on market |
|---|---|---|---|---|---|---|---|
| single_family | 6 | 7 | 8,202 | $368,050 | 2024-04-14 | — | |
| single_family | 6 | 5 | 3,356 | $21,400 | 2026-02-06 | — | |
| single_family | 6 | 6 | 4,007 | $27,000 | 2026-08-05 | — | |
| single_family | 6 | 9 | 4,757 | $21,500 | 2026-03-02 | — | |
| single_family | 6 | 7 | 6,433 | $75,000 | 2026-05-26 | — |
Same ZIP & bedroom count. Closed sales from Realtor.com over the last 12 months, matched to this property's type — real transaction prices, not asking prices. Falls back to Miami-Dade County public records (property appraiser tax roll) when Realtor.com has no sales on file for the area.
| Address | Type | Beds | Baths | Living sqft | Sale price | Sale date |
|---|---|---|---|---|---|---|
| 762 Fernwood Rd | single_family | 6 | 5 | 3,584 | $5,690,000 | 2026-06-15 |
| 285 Woodcrest Rd | single_family | 6 | 6 | 3,520 | $6,700,000 | 2026-04-22 |
| 635 Curtiswood Dr | single_family | 6 | 6 | 3,888 | $4,950,000 | 2026-04-20 |
| 180 Cape Florida Dr | single_family | 6 | 8 | 8,031 | $21,000,000 | 2026-02-26 |
| 320 Atlantic Rd | single_family | 6 | 7 | 5,275 | $8,200,000 | 2026-02-25 |
| 320 Woodcrest Rd | single_family | 6 | 5 | 3,737 | $5,220,000 | 2025-10-06 |
Same ZIP. Other properties currently for sale nearby — asking prices, not closed sale prices. Not a price comp; see Sold comps for actual transaction history.
| Address | Type | Beds | Baths | Sqft | Asking price | Days on market |
|---|---|---|---|---|---|---|
| 960 Mariner Dr | single_family | 6 | 10 | 7,742 | $19,500,000 | — |
| 420 Island Dr | single_family | 6 | 8 | 6,405 | $12,485,000 | — |
| 120 Knollwood Dr | single_family | 6 | 7 | 6,208 | $19,950,000 | — |
| 650 Curtiswood Dr | single_family | 6 | 5 | 3,356 | $5,199,000 | — |
| 31 Island Dr | single_family | 6 | 7 | 5,826 | $9,800,000 | — |
| 165 Hampton Ln | single_family | 6 | 9 | 3,842 | $8,250,000 | — |
| 110 Hampton Ln | single_family | 6 | 7 | 3,550 | $6,900,000 | — |
| 238 Buttonwood Dr | single_family | 6 | 7 | 4,190 | $8,500,000 | — |
10-year hold projection
IRR-4.9%
Equity multiple0.18x
Total return (10yr)-$597,081
| Year | Property value | NOI | Cash flow | Loan balance | Equity |
|---|---|---|---|---|---|
| 1 | $8,240,000 | $65,880 | -$443,857 | $6,330,610 | $1,909,390 |
| 2 | $8,487,200 | $69,017 | -$441,125 | $6,256,455 | $2,230,745 |
| 3 | $8,741,816 | $72,278 | -$438,280 | $6,177,207 | $2,564,609 |
| 4 | $9,004,070 | $75,666 | -$435,317 | $6,092,517 | $2,911,553 |
| 5 | $9,274,193 | $79,186 | -$432,233 | $6,002,012 | $3,272,181 |
| 6 | $9,552,418 | $82,843 | -$429,023 | $5,905,292 | $3,647,127 |
| 7 | $9,838,991 | $86,642 | -$425,682 | $5,801,929 | $4,037,062 |
| 8 | $10,134,161 | $90,588 | -$422,206 | $5,691,469 | $4,442,692 |
| 9 | $10,438,185 | $94,686 | -$418,590 | $5,573,423 | $4,864,762 |
| 10 | $10,751,331 | $98,941 | -$414,828 | $5,447,271 | $5,304,060 |
Assumes 3.0% annual rent growth, 2.5% expense growth, 3.0% appreciation, and a 6.0% selling cost at exit — all placeholder assumptions, not market-derived.