Do we run into any issues with having to not getting permits if the structure is already there?

If I were to rent out the second level, but the house is not permitted as a multi-family or mother daughter,  could I be personally liable if there was a fire?  

The owners have made additions to the property and didn't get the additional work permitted when they did it.

yes. i have spent weeks working on this deal. the seller is ready and my workers are too. already got total cost for all required permits for my area, also my comps are good.

My ~$800K development project (commercial) in a tier 1 county resulted from county initiatives, and the economic development group helped me with permits and plans but not financially.

TECHNICALLY, in some areas this work even requires a permit. 

Back then it was best to keep additions below 500sq/ft to decrease costs of permits etc.. check with Sonoma county permit office on specifics.

I have a pending sale on a 3 bedroom 1 bath craftsman single family home built in 1912, it has a non-permitted but livable basement with it's own full bath, sink & separate outside entrance.

Alternatively have your realtor get 10k off the selling price due to no permit and forget about it.

Wondering about the entire process, from gathering permits (if necessary, and would love clarity on this), to executing on the project.