Texas Gator said:
That's the kind of thing that I don't know. More like, updated the kitchens and bathrooms, but I'm not sure on whether those updates addressed things like that or just made things look a lot nicer at the surface level.
1920s and they would originally had knob & tube wiring. Nobody can see through walls so you would need to open the cover plates of each receptacle and switch to determine what has been updated and what has not. A normal house inspector is not going to take on that liability. An electrician will if you specifically ask him that's what you're wanting to know. Inspect the crawl space and/or attic too. Knob & tube is not necessarily a deal breaker. It is just really old and you would just want to add GFCI/AFCI combo breakers on those circuits (may not be possible in areas if they used california three ways). And adjust your offer accordingly.
Same with plumbing. They would have used galvanized which corrodes from the inside and develops pin hole leaks. You would want the plumber to go through the crawl space and/or attic to determine how much is original and how much is new. A normal house inspector can do this depending on his willingness.