Pick your city and what was built without a permit. See the steps, the papers, the city penalty, your ADU rights, and when tearing it out makes more sense.
Many people get this wrong: "Legalizing just means paying the permit fee." The fee is the small part. As-built plans, opening walls for the inspector and fixing what doesn't meet code usually cost several times the fee. Get a contractor to look before you file.
Ken can tell you who in your city draws as-built plans and how buyers react. No spam.
408-666-2825