2) ADU vs home addition: which solves your problem best?

Home addition

Best when you want more space for the primary household (bigger kitchen, expanded living room, additional bedroom suite) and you do not need a separate unit.

ADU

Best when you want separation: rental income, multigenerational living, guest privacy, or a dedicated work space with its own entry.

In many San Diego neighborhoods, an ADU is a more flexible investment because it can shift uses over time: guest house now, rental later, family suite in the future.