I don't agree with my fellow attorney, whom you consulted. Most real estate appraisers will tell you an illegal addition doesn't add much, if any, value because the city can order removal if it cannot be ''legalized'' with a building permit. The property tax assessor usually cannot appraise an illegal addition and assess additional property taxes on it. Many cities have this tax problem you describe. They know illegal additions exist, often providing excellent, safe low-income housing, but they can't tax those units without making them legal.
Some cities now allow legalized ''granny units'' or secondary apartments.
When that occurs, additional property taxes can be assessed on the market value of a formerly illegal unit. But I am not aware of how a city or county can go back to assess ''escaped property taxes'' on illegal additions that are later legalized. Q. As president of our condominium homeowner's association, I am very interested in limiting the number of rentals in our 45-unit complex. Several of our owners have expressed interest in your recent item about how too many rentals hurt resales because mortgage lenders won't lend if there are too many rentals. But some owners said they would feel discriminated against if they cannot rent their condos.