I'm not sure. No seismic retrofits, but plenty of small stuff. A new toilet is a given. In Ben Lomond, the local fire department demands a sprinkler system on new construction and major remodels.
No. The local ground loading would not tolerate a foundation where the entire load is concentrated at 4 points. On my clay hillside, I'm limited to 1000 lbs/sq-ft and I'm very close.
The lowest price 3 bedroom house for sale in the area is about $400,000. Property taxes will be about 2% plus fees or about $8,000/year. Most residents cannot afford to buy their own house because of the property tax increase (another side effect of Prop 13).
I have a few spreadsheets showing the county fees and deposits for various types of construction. The costs are reather depressing. A new house runs about $30,000 for the county and the water district. A small remodel is about $500 to $2,000. The things we were discussing falls in between. Add about $7,000 if the house is in an ecologically or archeologically sensitive area.
Expensive bureaucracy is the price of living in paradise.