The simple answer: other than Mobile Home and RV Parks, you can't.
However, thanks to new legislation in California, you can add an additional home in your back yard called an Additional Dwelling Unit (ADU). The ADU can be a tiny home as long as you follow the requirements of your local building department; meaning get a permit, build it right, pass an inspection with a building inspector (initially we were told there was a minimum square footage requirement of 400 or 450 sq/ft, which we now know is not correct. Based on information presented at the 2017 San Diego County ADU Status Conference the only square footage requirement is that you have at least one room with 72 square feet plus a bathroom, kitchen, and sleeping space).
For those who already have a piece of land with dreams of putting a tiny home on it... there's currently no legal way to do this. So, the folks you hear about that are doing it are flying under the radar.
The good news is there has been a growing number of towns that are updating their building codes and community planning to allow for tiny homes. Interested in seeing examples of their changes? Click here.
Want to help change this? Sign the petition: https://www.change.org/p/residents-within-the-county-of-san-diego-legalize-tiny-homes-in-san-diego
Get the latest information on the legality of tiny homes in San Diego.
Below you can find info from communities that have already made the changes. Let's learn from them.