It seems like every city, county, and state has its own rules, permits, and tax requirements for short-term rentals, and I’m finding it overwhelming to navigate all the different layers of compliance.For example, some places require business licenses, transient occupancy tax permits, or even special zoning approvals.

It sounds like you have an un-permitted unit, which is essentially always a risk since there has been no notice to the AHJ that it exists and they can therefore initiate a code case to have it removed in most cases.

I'd argue that there are very select zip codes where this strategy works.

My question is why you want to bring it up to code, other than just to feel good or improve your exit strategy?

Quote from @Jemini Leckie: Hello, I am trying to understand the Orem, city code to determine if I am allowed to rent my basement ADU that I currently live in two a couple cousins and their friend.

The bay area has many old houses so be aware of what it will take to being them up to code and meet insurance requirements.

Then add any other codes required where you want to build and study those as well.

These are professionals with additional training and a stricter code of ethics.

I was thinking of starting a rent increase for my 1 bedroom tenant voucher due it being low and well under fair market value(Based on  hud and zip code) but my tenant is in the process of having a caretaker for her disability and getting approved for a two bedroom voucher.

My thoughts:- best advice above is to get a good attorney that specializes in evictions. - Who ever told you that only 30 days notice is required does not know CA law.