An accessory dwelling unit can solve a housing problem without changing the address. It can also become an expensive answer to the wrong question.
The decision should begin with the outcome. Is the goal space for a parent, rental income, privacy for an adult child, future accessibility, or greater property flexibility?
The existing place has value
An ADU may make sense when the household wants to preserve the neighborhood, schools, commute, mortgage, community, or land. Moving may solve the space problem but sacrifice what already works.
The site must support the idea
Zoning is only one layer. Setbacks, lot shape, utilities, access, parking, trees, drainage, critical areas, and existing structures can affect what appears practical. Local research should be followed by verification from planning and qualified professionals.
The arrangement must work for people
Think about privacy, sound, entrances, outdoor space, caregiving, parking, and how the units will relate day to day. A technically permitted unit is not automatically a good living arrangement.
The economics require a full comparison
Include design, permits, utility work, financing, construction, contingency, temporary disruption, and ongoing ownership costs. Then compare those with the cost of selling, buying, moving, and accepting the compromises available in the market.
Future uses matter
Ask what happens if the family need changes. Could the unit become a rental, office, guest space, or caregiver residence? Verify local rental rules and avoid assuming every future use will be allowed.
An ADU makes more sense than moving when it supports the human outcome, fits the property, survives professional verification, and compares favorably with realistic alternatives.