So I'm looking at purchasing a 1920s duplex that has been mostly renovated. Unfortunately it seems like they didn't do any work on the foundation. It is a pier and beam and the floor in the lower unit is obviously sloped - it is highest in the middle and slopes down to the edges of the house. The access to the crawlspace is very small but I was able to get a video of it with a camera attached to a broomstick.

The beam that I could see is probably 6" off of the ground at best. I know that modern codes require 16"+. Will the entire house need to be raised? Will the edges need to be raised to level the floor? I've heard that houses with low crawlspaces may need tunnels dug under them to inspect/repair the foundation - do you think this would be necessary?

Any general insight on old pier and beam foundations is appreciated - I don't know alot about them or what is acceptable and what needs to be fixed.