Trulia Voices Question - Convert Campbell Detached Garage to Legal 2nd Unit?

Absolutely POSSIBLE - there have been many 2nd units done in the Campbell area legally. Of course, the City will require everything done according to code - while this may not sound unreasonable - the cost of making a true 2nd unit legal may cost far more than what you may want to spend. The best solution would be to check with an architect and have some plans drawn up. The architect will check with the City and see what needs to be done to make this legal. Some initial blocks that will come up that may derail the project are set back requirements of the structure. While the garage may be "grandfathered legal', any re-work to the space may trigger all new approvals and zoning compliance - 5' from side property lines, 20' from rear, etc. If you don't own the home yet, perhaps consider a duplex which was built legally as 2 units.