631 N Mashta Dr
Key Biscayne, FL 33149 · single_family · For Sale · 34 days on market
Asking price$18,500,000
4 beds 5 baths 2,255 sqft
Suggested offer$2,987,695$15,512,305 above the est. market value of $2,987,695.
View on Realtor.com →Listed by Javier G Quiroz · Coldwell Banker Realty
Typesingle_family
Built1958
Price / sqft$8204
Est. value (own analysis)$2,987,695
Rent estimate (own analysis)$14,900/mo
HOANone
1 / 50
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Statusfor_sale
Listed date2026-07-30
Removed date—
MLSBeachesMLS #B26058354
Coordinates25.68593, -80.17396
Address631 N Mashta Dr
CityKey Biscayne
StateFL
Zip33149
Listing ID6248723991
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 | $18,500,000 |
| Down payment (20.0%) | $3,700,000 |
| Loan amount | $14,800,000 |
| Closing costs (5.0%) | $925,000 |
| Total cash to close | $4,625,000 |
| Income | |
| Rent (comp-derived) | $14,900$178,800 |
| Vacancy loss (8.0%) | |
| Effective gross income | $13,708$164,496 |
| Operating expenses | |
| Property tax (placeholder 1.9% of price) | $29,292$351,500 |
| Insurance (placeholder 0.8% of price) | $12,333$148,000 |
| HOA dues | $0$0 |
| Management (0.0% of EGI) | $0$0 |
| Maintenance (5.0% of GSR) | $745$8,940 |
| Total operating expenses | $42,370$508,440 |
| 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) | $745$8,940 |
| 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 | 2 | 2,175 | $13,500 | 2026-02-09 | — | |
| single_family | 4 | 3 | 2,112 | $12,500 | 2026-02-04 | — | |
| single_family | 4 | 3 | 2,196 | $16,500 | 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 | — | |
| single_family | 4 | 3 | 1,798 | $13,500 | — | — | |
| single_family | 4 | 3 | 1,979 | $10,900 | 2026-08-10 | — |
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 | — |
| 445 Grand Bay Dr Apt 303 | condos | 4 | 5 | 3,480 | $3,850,000 | — |
| 350 E Ocean Dr Unit 301N | condos | 4 | 7 | 3,798 | $8,950,000 | — |
10-year hold projection
IRR-11.6%
Equity multiple-0.98x
Total return (10yr)-$6,758,058
| Year | Property value | NOI | Cash flow | Loan balance | Equity |
|---|---|---|---|---|---|
| 1 | $19,055,000 | -$343,944 | -$1,494,189 | $14,639,535 | $4,415,465 |
| 2 | $19,626,650 | -$351,720 | -$1,502,189 | $14,468,051 | $5,158,599 |
| 3 | $20,215,450 | -$359,666 | -$1,510,364 | $14,284,791 | $5,930,659 |
| 4 | $20,821,913 | -$367,785 | -$1,518,718 | $14,088,946 | $6,732,967 |
| 5 | $21,446,570 | -$376,081 | -$1,527,255 | $13,879,652 | $7,566,918 |
| 6 | $22,089,967 | -$384,557 | -$1,535,978 | $13,655,986 | $8,433,982 |
| 7 | $22,752,667 | -$393,218 | -$1,544,891 | $13,416,960 | $9,335,706 |
| 8 | $23,435,247 | -$402,066 | -$1,553,998 | $13,161,520 | $10,273,726 |
| 9 | $24,138,304 | -$411,106 | -$1,563,304 | $12,888,539 | $11,249,765 |
| 10 | $24,862,453 | -$420,342 | -$1,572,812 | $12,596,812 | $12,265,641 |
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.