Duplex Zoned for SFH (RS-1-7) in SD

[Luis Espinoza]

Hello! I'm look into a duplex in San Diego. When I pulled the county records, I noticed that the parcel is RS-1-7 zoning which from reading through the county municipal code is a zone for single dwelling units. I did some more research and learned about California's SB9 which from what I understood would make it possible for there to be a duplex in a parcel zoned for SFH.

The weird thing is that the duplex appears to have been built a LONG time ago and SB9 was just recently passed.

Does that mean the owner had an unpermitted duplex for years and it was recently legalized by the passing of SB9? Are there records that the owner would have needed to file with the county to register the duplex under SB9?

The current seller bought it in 2017 if that helps with anything. 

Thank you!