Legal Question in Real Estate Law in California

Whether it is a manufactured home, stick-built home, recreational vehicle, motor home, recreational vehicle, SUV, automobile, car or truck doesn't matter. When it becomes attached to the real estate and is used as a residence, it will be taxed as part of the real estate, and will also be subject to all zoning laws and regulations applicable to that parcel. I would encourage you to have a discussion with county planning and permitting personnel to get a clearer idea of what they'll allow on your parcel without your having to apply for a variation, what might be granted if you applied for a variation, and what the effect might be on your property taxes. It's possible that the added value of your property might make it a worth-while project even if your taxes went up. Consider the additional rental value of the second unit, for example, or if you are planning to sell within a few years, consider the increase in value (ask a licensed real estate pro about this aspect).