Owner Move-in Eviction

[Bruce Ng]

Working on acquiring a triplex. 
All units by code are 1bd/1ba, but one was converted to a 3bd. It does not appear to be permitted. 
One of the 1/1's is vacant. I am planning to househack it and move into the 3/1 with my girlfriend (soon to be fiancé hopefully). Both occupied units are paying well under half market rate.

If the 3/1 tenants don't agree to a cash-for-keys agreement, is there anything I should be mindful of when executing an owner move-in eviction in this situation? 

I understand I would need to live there for 2 years.
I would want to live in the larger unit because I work from home and the lady has her own business too, but since it's likely not permitted, would there be any issues? 

This would be in Los Angeles County. 

Thanks all for any insights!