What are the pros and cons of building an ADU?

Building an Accessory Dwelling Unit (ADU) in 2026 offers a path to increased property value and rental income, balanced against high upfront costs and complex regulations. 

Pros of Building an ADU

• Rental Income Generation: ADUs can provide consistent passive income. In high-demand markets like California, monthly rents for ADUs often range from $1,500 to $3,500.
• Significant Property Value Increase: Adding an ADU can increase a home’s market value by 20% to 35%. In some competitive markets, this can translate to adding over $250,000 in equity.
• Flexible Use Case: They provide private living spaces for multi-generational families (e.g., aging parents or adult children), guest houses, or dedicated home offices.
• Tax Benefits for Landlords: Homeowners who rent out their ADU may be able to deduct maintenance, utility costs, mortgage interest, and building depreciation (typically over 27.5 years).
• Environmental & Community Impact: ADUs utilize existing land and infrastructure (“gentle density”), promoting more sustainable urban development and helping address housing shortages. 

Cons of Building an ADU

• High Upfront Costs: Average construction costs in 2026 typically range from $150,000 to over $400,000 for new detached units. Even garage conversions can cost between $80,000 and $150,000.
• Increased Property Taxes: Building an ADU will raise your property tax bill. In California, this is generally calculated as roughly 1% of the ADU’s assessed value. For example, a $150,000 ADU adds about $1,500 annually to taxes.
• Complex Permitting and Zoning: Navigating local regulations, setbacks, and utility hookups can be a lengthy and expensive process. “Soft costs” like design and permits alone can range from $8,000 to $30,000+.
• Reduced Privacy and Space: Adding a secondary unit often requires sacrificing yard or garage space and may lead to increased noise and reduced privacy due to shared outdoor areas.
• Ongoing Management: Homeowners must take on the responsibilities of a landlord, including tenant management, regular maintenance, and repairs for a second residential unit.