Most are fine with that, but a few will have problems with it and claim there are legal issues, etc..

Are you aware of city of San Diego rules regarding converting existing legal space to ADUs?  

Quote from @Michael Baum: Hey @Dina Schmid, so legally a bedroom requires a closet and an egress window.

I would not make this a legal matter, but you will have to decide if you want to commit to living with this landlord.

As an investor, I’ve had multiple sellers try to get out of an agreement after we had a legally executed mutually agreed upon sales/purchase agreement.

Indeed, the FAIR ordinance is anything but fair to non-corporate landlords, seemingly punished for investing in rental houses to generate income as an alternative to stocks and bonds.A handful of opportunists likely could learn to exploit these new rules, preying on otherwise law-abiding landlords to obtain legalized shake-down payments.

If you need financial help, ask under the "Finance, Tax, and Legal" forum.

Can you buy a house with a legal suite?  

You may consider terminating the lease depending on how much time remains, your skills, the legal system, and other factors.Based on what you've said, I am concerned there's someone else occupying the home or something else is going on.

Do not rely on it for legal advice.