Previously Multi-Family Property Grandfather In. Value?

[Mike H.]

Hello.

I am interested in a 100y old multi-family property (3 units, 400sqft, 700sqft, 2600sqft). It was conforming when built. The zoning is now changed to SF, but the property is grandfathered in and can keep being used as multi-family. In case of a natural disaster (fire), the property will be tough to rebuild as a multi-family (chances are the city, San Diego will only allow a permit for SF). I can do improvements, remodels (up to 50% market value) without issues, but no tear down.

I am having a hard time coming up with comps. Should I use SF as comps? or MF ? or SF + an extra %?

The neighborhood is 95% SF which is a plus.
Thanks in advance