685 Harbor Ln
Key Biscayne, FL 33149 · single_family · For Sale · 139 days on market
Asking price$6,950,000
5 beds 6 baths 5,421 sqft
Listed by Marisela Gonzalez Servat · Avanti Way
Typesingle_family
Built2001
Price / sqft$1282
Est. value (own analysis)$7,756,073
Rent estimate (own analysis)$32,000/mo
HOANone
1 / 46
Show every detail
Statusfor_sale
Listed date2026-04-16
Removed date—
MLSMiamiMLS #A11997896
Coordinates25.68827, -80.17116
Address685 Harbor Ln
CityKey Biscayne
StateFL
Zip33149
Listing ID6220029215
Sourceus-real-estate-listings, cached 2026-08-28
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 | $6,950,000 |
| Down payment (20.0%) | $1,390,000 |
| Loan amount | $5,560,000 |
| Closing costs (5.0%) | $347,500 |
| Total cash to close | $1,737,500 |
| Income | |
| Rent (comp-derived) | $32,000$384,000 |
| Vacancy loss (8.0%) | |
| Effective gross income | $29,440$353,280 |
| Operating expenses | |
| Property tax (placeholder 1.9% of price) | $11,004$132,050 |
| Insurance (placeholder 0.8% of price) | $4,633$55,600 |
| HOA dues | $0$0 |
| Management (0.0% of EGI) | $0$0 |
| Maintenance (5.0% of GSR) | $1,600$19,200 |
| Total operating expenses | $17,238$206,850 |
| 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) | $1,600$19,200 |
| 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 | 3,650 | $28,500 | 2026-05-19 | — | |
| single_family | 5 | 6 | 5,421 | $25,000 | 2026-08-03 | — | |
| single_family | 5 | 6 | 3,661 | $55,000 | 2026-07-20 | — | |
| single_family | 5 | 6 | 3,633 | $21,500 | 2026-05-21 | — | |
| single_family | 5 | 6 | 5,341 | $70,000 | 2025-05-26 | — | |
| single_family | 5 | 6 | 4,700 | $35,500 | 2026-03-18 | — |
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 | — |
| 524 Warren Ln | single_family | 5 | 4 | 2,700 | $3,730,000 | — |
| 445 Grand Bay Dr Ph 1A | condos | 5 | 6 | 8,435 | $18,900,000 | — |
10-year hold projection
IRR-1.6%
Equity multiple0.74x
Total return (10yr)$447,731
| Year | Property value | NOI | Cash flow | Loan balance | Equity |
|---|---|---|---|---|---|
| 1 | $7,158,500 | $146,430 | -$301,531 | $5,499,717 | $1,658,783 |
| 2 | $7,373,255 | $151,857 | -$296,584 | $5,435,295 | $1,937,960 |
| 3 | $7,594,453 | $157,473 | -$291,460 | $5,366,448 | $2,228,004 |
| 4 | $7,822,286 | $163,284 | -$286,153 | $5,292,874 | $2,529,412 |
| 5 | $8,056,955 | $169,296 | -$280,658 | $5,214,248 | $2,842,707 |
| 6 | $8,298,663 | $175,517 | -$274,967 | $5,130,222 | $3,168,442 |
| 7 | $8,547,623 | $181,952 | -$269,075 | $5,040,425 | $3,507,198 |
| 8 | $8,804,052 | $188,610 | -$262,973 | $4,944,463 | $3,859,589 |
| 9 | $9,068,174 | $195,498 | -$256,656 | $4,841,911 | $4,226,263 |
| 10 | $9,340,219 | $202,623 | -$250,116 | $4,732,316 | $4,607,903 |
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.