It can be a solid move when the numbers genuinely work. The catch is that most people underestimate what it takes. Converting an existing detached garage usually costs less than building a new structure from scratch, and done right it adds both rental income and equity. What gets misjudged: - Cost and timeline. Plumbing, electrical, and permitting add up fast, and the approval process alone can stretch longer than anyone expects. - Value added. People tend to overestimate how much the unit adds to the property, so run conservative numbers on the build cost, the realistic rent, and the resale bump before you commit. - The lot. Cramming a unit onto a small lot, or giving up all the parking and yard to do it, can hurt resale later even when the rent looks good on paper. On the right lot there are options beyond a straight conversion, like building above the existing garage so you keep parking below. Rules are local, so check them first. In California, state law generally allows garage conversions and ADUs, but individual cities set their own codes and some are far more painful to work through than others, and an HOA can layer on its own restrictions. Confirm the requirements and process with your specific city (and HOA, if you have one) before you count on the income. If you're weighing a purchase partly for its ADU potential, price that out carefully as part of the buying decision, and it's something we're happy to help you think through.