690 Warren Ln
Key Biscayne, FL 33149 · single_family · For Sale · 125 days on market
Asking price$5,478,000
4 beds 4 baths 3,549 sqft
Suggested offer$4,702,141$775,859 above the est. market value of $4,702,141.
View on Realtor.com →Listed by Brigitte Nachtigall · One Sotheby's International Realty
Typesingle_family
Built2000
Price / sqft$1544
Est. value (own analysis)$4,702,141
Rent estimate (own analysis)$19,000/mo
HOANone
1 / 40
Show every detail
Statusfor_sale
Listed date2026-04-30
Removed date—
MLSMiamiMLS #A12010108
Coordinates25.68874, -80.16927
Address690 Warren Ln
CityKey Biscayne
StateFL
Zip33149
Listing ID6238587655
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 | $5,478,000 |
| Down payment (20.0%) | $1,095,600 |
| Loan amount | $4,382,400 |
| Closing costs (5.0%) | $273,900 |
| Total cash to close | $1,369,500 |
| Income | |
| Rent (comp-derived) | $19,000$228,000 |
| Vacancy loss (8.0%) | |
| Effective gross income | $17,480$209,760 |
| Operating expenses | |
| Property tax (placeholder 1.9% of price) | $8,674$104,082 |
| Insurance (placeholder 0.8% of price) | $3,652$43,824 |
| HOA dues | $0$0 |
| Management (0.0% of EGI) | $0$0 |
| Maintenance (5.0% of GSR) | $950$11,400 |
| Total operating expenses | $13,276$159,306 |
| 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) | $950$11,400 |
| 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 | 4 | 3 | 2,749 | $19,000 | 2026-08-25 | — | |
| single_family | 4 | 5 | 3,202 | $31,500 | 2026-07-24 | — | |
| single_family | 4 | 3 | 2,316 | $14,900 | 2026-06-27 | — | |
| single_family | 4 | 4 | 3,006 | $18,900 | 2026-07-29 | — | |
| single_family | 4 | 3 | 2,406 | $19,000 | 2026-05-29 | — |
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 |
|---|---|---|---|---|---|---|
| 301 Hampton Ln | single_family | 4 | 3 | 2,068 | $3,100,000 | 2026-08-24 |
| 591 N Mashta Dr | single_family | 4 | 5 | 4,290 | $14,000,000 | 2026-08-03 |
| 217 Buttonwood Dr | single_family | 4 | 3 | 2,503 | $3,500,000 | 2026-06-23 |
| 401 Warren Ln | single_family | 4 | 3 | 2,958 | $3,000,000 | 2026-04-20 |
| 465 Hampton Ln | single_family | 4 | 4 | 3,666 | $4,475,000 | 2026-04-10 |
| 760 Glenridge Rd | single_family | 4 | 6 | 4,142 | $625,000 | 2026-04-09 |
| 315 Palmwood Ln | single_family | 4 | 5 | 3,297 | $4,400,000 | 2026-04-08 |
| 285 W Enid Dr | single_family | 4 | 3 | 3,436 | $4,200,000 | 2026-04-02 |
| 340 Ridgewood Rd | single_family | 4 | 3 | 2,699 | $3,550,000 | 2026-03-12 |
| 600 Allendale Rd | single_family | 4 | 4 | 2,775 | $3,500,000 | 2026-01-16 |
| 361 W Heather Dr | single_family | 4 | 3 | 1,570 | $2,600,000 | 2025-09-19 |
| 92 W Mashta Dr | single_family | 4 | 3 | 2,403 | $3,230,000 | 2025-09-12 |
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 |
|---|---|---|---|---|---|---|
| 200 Ocean Lane Dr Apt 501 | condos | 4 | 4 | 1,880 | $3,850,000 | — |
| 201 Crandon Blvd Apt 174 | townhomes | 4 | 6 | 3,254 | $5,100,000 | — |
| 255 Ridgewood Rd | single_family | 4 | 3 | 2,177 | $3,550,000 | — |
| 100 Cape Florida Dr | single_family | 4 | 9 | 8,240 | $19,800,000 | — |
| 161 Cape Florida Dr | single_family | 4 | 6 | 6,661 | $14,990,000 | — |
| 640 S Mashta Dr | single_family | 4 | 4 | 3,620 | $16,800,000 | — |
| 631 N Mashta Dr | single_family | 4 | 5 | 2,255 | $18,500,000 | — |
| 445 Grand Bay Dr Apt 303 | condos | 4 | 5 | 3,480 | $3,850,000 | — |
10-year hold projection
IRR-4.7%
Equity multiple0.22x
Total return (10yr)-$350,964
| Year | Property value | NOI | Cash flow | Loan balance | Equity |
|---|---|---|---|---|---|
| 1 | $5,642,340 | $50,454 | -$298,896 | $4,334,885 | $1,307,455 |
| 2 | $5,811,610 | $52,764 | -$296,871 | $4,284,107 | $1,527,503 |
| 3 | $5,985,959 | $55,164 | -$294,763 | $4,229,842 | $1,756,116 |
| 4 | $6,165,537 | $57,655 | -$292,571 | $4,171,851 | $1,993,686 |
| 5 | $6,350,503 | $60,243 | -$290,291 | $4,109,878 | $2,240,626 |
| 6 | $6,541,018 | $62,929 | -$287,919 | $4,043,648 | $2,497,370 |
| 7 | $6,737,249 | $65,718 | -$285,452 | $3,972,871 | $2,764,378 |
| 8 | $6,939,367 | $68,614 | -$282,887 | $3,897,233 | $3,042,133 |
| 9 | $7,147,548 | $71,619 | -$280,221 | $3,816,402 | $3,331,146 |
| 10 | $7,361,974 | $74,738 | -$277,449 | $3,730,019 | $3,631,955 |
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.