Remodeled Duplex with Cottage
For Sale
$999,950
4231 Somerset Ave, Castro Valley, CA 94546
Residential Income, Castro Valley, CA
Property Size1,285 SF
Lot Size0.12 Acres
Price / SF$778.17
Days on Market52
Property Features for 4231 Somerset Ave
General Information
Property type
Residential Multi Family
Property subtype
Other
Bedrooms
3
Bathrooms
1
Full bathrooms
1
Rooms
Bathroom 1, Bedroom 2, Bedroom 3, Bedroom 1, Laundry Room
Parking features
Carport
Window features
Double Pane Windows
Interior features
Shower Stall(s)
Exterior features
Back Yard, Front Yard, Storage, Landscape Front
Fencing
Fenced
Subdivision
Castro Valley
Lot features
2 Houses / 1 Lot
Directions
Redwood Rd to Somerset
Standard status
Active
APN
84C75732
Size
1,285 SF
Lot size
0.12 Acres
Utilities
Sewer type
Public Sewer
Heating system
Forced Air, Wall Furnace
Cooling system
Central Air
Water source
Private
Building Details
Year built
1949
Number of units
2
Flooring type
Laminate, Hardwood, Tile, Carpet
Building materials
Stucco
Roof type
Composition, Rolled Hot Mop
Additional Structures
Storage
Listing Agency:
EXP Realty of California, Inc
(888) 584-9427
Listed By:
Tim Fiebig · License #00657474
(510) 708-8700
Added: Jul 9
Changed: Aug 27
Last Checked: Aug 29 at 12:06AM
MLS# 41141107
Copyright © 2026 Bay East. All rights reserved. All information provided by the listing agent/broker is deemed reliable but is not guaranteed and should be independently verified.
Investment Insights
Based on property information with market context.
This duplex property combines a remodeled three-bedroom, one-bath main residence with a detached 250-square-foot studio cottage featuring its own laundry. The primary home includes 1,035 square feet, hardwood flooring through much of the interior, tile in select areas, and an updated kitchen with Corian countertops, wood cabinetry, a four-burner gas range, and built-in microwave. A dedicated laundry room adds substantial built-in storage. The living room features a tray ceiling, crown molding, and LED lighting.
Outdoor improvements include a patio deck, fenced backyard with lawn, front and rear landscaping, and a matching storage shed. The cottage is separately fenced and currently rented, while also offering flexibility for guests, a home office, or extended household use. Additional property features include a carport, central air, forced-air and wall-furnace heating, public sewer, and a 1949 construction date.
Outdoor improvements include a patio deck, fenced backyard with lawn, front and rear landscaping, and a matching storage shed. The cottage is separately fenced and currently rented, while also offering flexibility for guests, a home office, or extended household use. Additional property features include a carport, central air, forced-air and wall-furnace heating, public sewer, and a 1949 construction date.
Key Highlights
- 1,035‑square‑foot, three‑bedroom primary residence with one bathroom
- Detached 250‑square‑foot studio cottage with laundry
- Cottage is separately fenced and currently rented
Financial Insights
Estimated NOI and Cap Rate
NOI = area × lease_rate × (100 − vacancy) / 100 × (1 − expense_ratio). Net Operating Income — what the owner takes home each year before mortgage payments and income tax. Effective rent (asking rent minus vacancy losses) minus operating costs (taxes, insurance, maintenance, management).
NOI / Yr
$43,131
Cap rate = NOI / list price × 100. Capitalization rate — annual return on a fully cash purchase, before financing. NOI divided by price. Higher means more income per dollar invested, but usually also more risk or older condition. 5–8% is typical for stabilized commercial property; double digits often signal distressed deals.
Cap Rate
4.31%
Suggested Prices Based on Cap Rates
Cap rates vary significantly by property type, market, and asset quality.
Typical U.S. stable-market ranges:
Multifamily — 4.5% to 6.5% (Class A in primary markets often sub-5%; Class C in secondary markets 6%+)
Industrial / Logistics — 5.0% to 7.0% (compressed heavily in recent years due to e-commerce demand)
Office — 6.5% to 9%+ (wide spread post-2020; CBD Class A vs. suburban Class B varies dramatically)
Retail — 5.5% to 8.5% (grocery-anchored on the low end, unanchored strip centers higher)
Hospitality / Hotels — 7.5% to 10%+ (higher due to operational risk)
Self-Storage — 5.5% to 7.5%
Medical Office — 6.0% to 7.5%
Net Lease (single tenant, credit) — 5.0% to 7.0% depending on tenant credit and lease term
Rules of thumb:
Primary markets (NYC, SF, LA, Boston, DC) trade at lower cap rates than secondary/tertiary markets, often by 100–200 bps (bps, aka basis points; 1 bp = 0.01%).
Class A assets trade ~50–150 bps tighter than Class B, and Class B tighter than Class C.
Cap rates move inversely with price — a lower cap rate means a higher price for the same NOI.
Spread to the 10-year Treasury is a common benchmark; historically 200–400 bps over the 10-year.
Cap Rate 5%
$862,620
$862.6K
Cap Rate 7%
$616,157
$616.2K
Cap Rate 9%
$479,233
$479.2K
Market Conditions
NOI Build-Up for 1,285 SF
Vacancy — income lost from leasable area expected to sit empty during the year, subtracted from gross rent.
EGI (Effective Gross Income) — gross rent minus vacancy losses, the realistic income before paying operating costs.
OpEx (Operating Expenses) — recurring costs to operate the property (property tax, insurance, utilities, maintenance, management); excludes financing and capital improvements.
NOI (Net Operating Income) — income a property generates after operating costs but before financing and taxes.
Gross rent
$65.5K $51.00/SF
− Vacancy
−$3.9K −$3.05/SF
EGI
$61.6K $47.95/SF
− OpEx
−$18.5K −$14.39/SF
NOI
$43.1K $33.57/SF
Area
Alameda County, CA
Vacancy
5.98%
Lease Rate
$51.00 /SF/Yr
Expense Ratio
30.00%
Simulate Cap Rate and NOI
Suggested Prices Based on Cap Rates
Cap rates vary significantly by property type, market, and asset quality.
Typical U.S. stable-market ranges:
Multifamily — 4.5% to 6.5% (Class A in primary markets often sub-5%; Class C in secondary markets 6%+)
Industrial / Logistics — 5.0% to 7.0% (compressed heavily in recent years due to e-commerce demand)
Office — 6.5% to 9%+ (wide spread post-2020; CBD Class A vs. suburban Class B varies dramatically)
Retail — 5.5% to 8.5% (grocery-anchored on the low end, unanchored strip centers higher)
Hospitality / Hotels — 7.5% to 10%+ (higher due to operational risk)
Self-Storage — 5.5% to 7.5%
Medical Office — 6.0% to 7.5%
Net Lease (single tenant, credit) — 5.0% to 7.0% depending on tenant credit and lease term
Rules of thumb:
Primary markets (NYC, SF, LA, Boston, DC) trade at lower cap rates than secondary/tertiary markets, often by 100–200 bps (bps, aka basis points; 1 bp = 0.01%).
Class A assets trade ~50–150 bps tighter than Class B, and Class B tighter than Class C.
Cap rates move inversely with price — a lower cap rate means a higher price for the same NOI.
Spread to the 10-year Treasury is a common benchmark; historically 200–400 bps over the 10-year.
Cap Rate 5%
$862,620
Cap Rate 7%
$616,157
Cap Rate 9%
$479,233
Alternative Uses
Best Use
Multifamily LT 5
$616.2K
$539.1K – $718.9K
NOI $43,131 @ 7.0% cap · market cap 4.31%
Second Best
Apartment 5plus
$265.9K
$232.7K – $310.3K
NOI $18,615 @ 7.0% cap · market cap 1.86%
Theoretical Best
Retail
$5.86M
$5.13M – $6.83M
NOI $410,078 @ 7.0% cap · market cap 41.01%
Zoning and permitted uses should be independently verified with authorities.
Property Analytics
Property Profile
Current Use
Lease Details
2
Residential units
Location Intelligence
Trade Area within ½ mile
1,361
Businesses Nearby
Explore this area
Business Placement
Demographics for 94546, CA
46,687
Population
16,398
Households
2.8
Avg Household Size
40
Median Age
41%
College-Educated
90%
High-School Grad
16.0 sq mi
ZIP Area
2,918
Density / Sq Mi
$125,780
Median Household Income
$66,737
Median Earnings
$2,506
Median Rent
$976,300
Median Home Value
Market
Vacancy Rate% for Multifamily in West region
Questions? Ask Rey
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Frequently Asked Questions
What type of property is this?
Duplex - Updated primary residence with a separately fenced detached cottage, private outdoor space, and flexible additional living accommodations.
Where is this duplex located?
The property is located at 4231 Somerset Ave Castro Valley, CA.
What is the asking price?
The asking price for this property is $999,950.
What are key features of this property?
This property features: 1,035‑square‑foot, three‑bedroom primary residence with one bathroom; Detached 250‑square‑foot studio cottage with laundry; Cottage is separately fenced and currently rented
