524 Warren Ln
Key Biscayne, FL 33149 · single_family · For Sale · 144 days on market
Asking price$3,730,000
5 beds 4 baths 2,700 sqft
Listed by Fabrice Ernandes · Serhant
Typesingle_family
Built1950
Price / sqft$1381
Est. value (own analysis)$3,863,014
Rent estimate (own analysis)$22,000/mo
HOANone
1 / 62
Show every detail
Statusfor_sale
Listed date2026-04-11
Removed date—
MLSMiamiMLS #A11999112
Coordinates25.69166, -80.16921
Address524 Warren Ln
CityKey Biscayne
StateFL
Zip33149
Listing ID6071077243
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 | $3,730,000 |
| Down payment (20.0%) | $746,000 |
| Loan amount | $2,984,000 |
| Closing costs (5.0%) | $186,500 |
| Total cash to close | $932,500 |
| Income | |
| Rent (comp-derived) | $22,000$264,000 |
| Vacancy loss (8.0%) | |
| Effective gross income | $20,240$242,880 |
| Operating expenses | |
| Property tax (placeholder 1.9% of price) | $5,906$70,870 |
| Insurance (placeholder 0.8% of price) | $2,487$29,840 |
| HOA dues | $0$0 |
| Management (0.0% of EGI) | $0$0 |
| Maintenance (5.0% of GSR) | $1,100$13,200 |
| Total operating expenses | $9,493$113,910 |
| 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) | $1,100$13,200 |
| 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 | 5 | 6 | 3,495 | $20,000 | 2026-06-10 | — | |
| single_family | 5 | 5 | 3,202 | $40,000 | 2026-03-28 | — | |
| single_family | 5 | 6 | 3,633 | $21,500 | 2026-05-21 | — | |
| single_family | 5 | 5 | 3,149 | $22,000 | 2026-07-01 | — | |
| single_family | 5 | 7 | 3,475 | $27,500 | 2026-05-21 | — |
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 |
|---|---|---|---|---|---|---|
| 346 Gulf Rd | single_family | 5 | 6 | 3,285 | $4,700,000 | 2026-07-27 |
| 677 Hampton Ln | single_family | 5 | 4 | 2,429 | $3,125,000 | 2026-03-09 |
| 670 Allendale Rd | single_family | 5 | 5 | 2,320 | $3,475,000 | 2026-01-27 |
| 261 Greenwood Dr | single_family | 5 | 6 | 3,525 | $6,275,000 | 2025-12-11 |
| 201 Buttonwood Dr | single_family | 5 | 5 | 3,791 | $5,265,000 | 2025-12-09 |
| 100 Hampton Ln | single_family | 5 | 6 | 3,584 | $6,200,000 | 2025-12-04 |
| 220 Cypress Dr | single_family | 5 | 6 | 4,089 | $4,600,000 | 2025-10-10 |
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 |
|---|---|---|---|---|---|---|
| 485 W Matheson Dr | single_family | 5 | 9 | 11,528 | $237,000,000 | — |
| 501 Bay Ln | single_family | 5 | 5 | 4,759 | $5,990,000 | — |
| 520 S Mashta Dr | single_family | 5 | 4 | 3,085 | $19,900,000 | — |
| 571 Glenridge Rd | single_family | 5 | 7 | 3,768 | $7,490,000 | — |
| 545 Sabal Palm Dr | single_family | 5 | 5 | 4,166 | $7,950,000 | — |
| 24 Grand Bay Estates Cir | single_family | 5 | 6 | 4,220 | $4,950,000 | — |
| 445 Grand Bay Dr Ph 1A | condos | 5 | 6 | 8,435 | $18,900,000 | — |
| 445 Ridgewood Rd | single_family | 5 | 6 | 3,688 | $6,685,000 | — |
10-year hold projection
IRR2.0%
Equity multiple1.32x
Total return (10yr)$786,185
| Year | Property value | NOI | Cash flow | Loan balance | Equity |
|---|---|---|---|---|---|
| 1 | $3,841,900 | $128,970 | -$114,342 | $2,951,647 | $890,253 |
| 2 | $3,957,157 | $133,409 | -$110,233 | $2,917,072 | $1,040,085 |
| 3 | $4,075,872 | $137,995 | -$105,985 | $2,880,123 | $1,195,749 |
| 4 | $4,198,148 | $142,733 | -$101,594 | $2,840,636 | $1,357,512 |
| 5 | $4,324,092 | $147,628 | -$97,054 | $2,798,438 | $1,525,655 |
| 6 | $4,453,815 | $152,686 | -$92,361 | $2,753,342 | $1,700,473 |
| 7 | $4,587,430 | $157,911 | -$87,509 | $2,705,149 | $1,882,280 |
| 8 | $4,725,052 | $163,309 | -$82,494 | $2,653,647 | $2,071,406 |
| 9 | $4,866,804 | $168,885 | -$77,310 | $2,598,608 | $2,268,196 |
| 10 | $5,012,808 | $174,645 | -$71,952 | $2,539,789 | $2,473,019 |
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.