You should have a form titled WPA with your purchase contract. It will state who is responsible for the Section 1/ Section 2 work in CA.
Most often the seller pays for section 1, buyer Section 2. However many different terms can be written in the WPA. For condos, when I'm the listing agent, I get interior only reports. That is all my seller is responsible for (walls in no attic space). As everyone else already, walls-out is the responsibility of the HOA (usually).
Definitely ask your agent. I'm sure they will be able to better understand your particular situation.