Converting a garage into an ADU generally adds significant value to a house by increasing property value and generating rental income. The value increase can be up to 35%, depending on the size and type of ADU, build quality, and local housing market conditions. Detached ADUs typically add more value than attached or interior conversions. High-quality materials and unique features further enhance value. Rental income from an ADU can offset conversion costs, potentially yielding substantial financial returns over time. However, conversion costs range from $80,000 to $250,000, including permits and compliance with local regulations. Despite these costs, the long-term financial benefits often justify the investment.