Or if I'm lucky, there's hardwood underneath that can just be refinished

One thing I can tell you is check for a soils report if you are in west LA, most likely you are on a hill and building setbacks such as H/3 requirements can really drive the cost of your foundation up.

(REMEMBER THIS ALWAYS) You have greatness in you,(YOU ARE ALREADY CREATE LIKE THIS< WITH GREATNESS)  just like a seed. ( a seed) doesn't say I am just a seed, a seed has potential inside, it just needs the correct environment and timing and condition to become GREAT and ABLE to create fruit, It needs, Soil, Water, and correct temperature to grow (and time) .

There are certain neighborhoods that have notoriously bad foundation issues due to the soil composition.

Rima and I keep people out of trouble with the highly-regulated toxic and hazardous materials - asbestos, lead, VOCs, soil and groundwater contamination, plus indoor air quality and the almost unregulated mold.  

Underneath it is unemployment, mounting consumer debt and permanently closed businesses.

Eventually you need structural engineering, a survey and a soils report.  

Account Closed - not sure if it's required to build an ADU in San Fernando, but a bunch of cities in the Bay Area require a soils report from a Geotechnical Engineer for new construction like ADUs.

But if you seal down the replacement patch you put in down hard to the shingles underneath with good sealant as you go, your problems, if they're anything like mine, are all over for a very long time.I wouldn't deal with getting the seller to address the leaks at all.

I guess but i would have to see that.. thats pretty crazy.. you let houses sit like that in those weather conditions and soil conditions with out regular maintenance they will get either broken into and stripped or squatters or foundations will go wonky..