520 S Mashta Dr
Key Biscayne, FL 33149 · single_family · For Sale · 16 days on market
Asking price$19,900,000
5 beds 4 baths 3,085 sqft
Suggested offer$4,413,851$15,486,149 above the est. market value of $4,413,851.
View on Realtor.com →Listed by Maureen Jauregui · Coldwell Banker Realty
Typesingle_family
Built1961
Price / sqft$6451
Est. value (own analysis)$4,413,851
Rent estimate (own analysis)$27,500/mo
HOANone
1 / 39
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Statusfor_sale
Listed date2026-08-17
Removed date—
MLSMiamiMLS #A12071221
Coordinates25.68330, -80.17270
Address520 S Mashta Dr
CityKey Biscayne
StateFL
Zip33149
Listing ID6245407322
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 | $19,900,000 |
| Down payment (20.0%) | $3,980,000 |
| Loan amount | $15,920,000 |
| Closing costs (5.0%) | $995,000 |
| Total cash to close | $4,975,000 |
| Income | |
| Rent (comp-derived) | $27,500$330,000 |
| Vacancy loss (8.0%) | |
| Effective gross income | $25,300$303,600 |
| Operating expenses | |
| Property tax (placeholder 1.9% of price) | $31,508$378,100 |
| Insurance (placeholder 0.8% of price) | $13,267$159,200 |
| HOA dues | $0$0 |
| Management (0.0% of EGI) | $0$0 |
| Maintenance (5.0% of GSR) | $1,375$16,500 |
| Total operating expenses | $46,150$553,800 |
| 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) | $1,375$16,500 |
| 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 | 3,495 | $20,000 | 2026-06-10 | — | |
| single_family | 5 | 6 | 3,661 | $55,000 | 2026-07-20 | — | |
| 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 | — |
| 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 | — |
| 445 Ridgewood Rd | single_family | 5 | 6 | 3,688 | $6,685,000 | — |
10-year hold projection
IRR-10.1%
Equity multiple-0.72x
Total return (10yr)-$5,971,749
| Year | Property value | NOI | Cash flow | Loan balance | Equity |
|---|---|---|---|---|---|
| 1 | $20,497,000 | -$250,200 | -$1,494,375 | $15,747,392 | $4,749,608 |
| 2 | $21,111,910 | -$254,937 | -$1,499,524 | $15,562,930 | $5,548,980 |
| 3 | $21,745,267 | -$259,747 | -$1,504,757 | $15,365,802 | $6,379,465 |
| 4 | $22,397,625 | -$264,630 | -$1,510,073 | $15,155,136 | $7,242,489 |
| 5 | $23,069,554 | -$269,587 | -$1,515,475 | $14,930,004 | $8,139,550 |
| 6 | $23,761,641 | -$274,618 | -$1,520,961 | $14,689,412 | $9,072,229 |
| 7 | $24,474,490 | -$279,724 | -$1,526,533 | $14,432,298 | $10,042,192 |
| 8 | $25,208,725 | -$284,904 | -$1,532,192 | $14,157,528 | $11,051,197 |
| 9 | $25,964,986 | -$290,160 | -$1,537,938 | $13,863,888 | $12,101,098 |
| 10 | $26,743,936 | -$295,491 | -$1,543,772 | $13,550,085 | $13,193,851 |
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.