Legal Question in Real Estate Law in California

Re: The most frightening thought of my life!

Who occupies the other half of the duplex, the grandson? The situation you describe is frightening indeed, with an irresponsible person like this grandson as an occupant, not to mention the state's prospective claim on the co-tenant's half interest.

In my opinion, your mother needs competent LOCAL legal assistance. Her interest in the property is doubtless worth enough, and sufficiently threatened, to warrant spending on a few hours of attorney time.

In general, the interests of tenants in common are protected from the debts of the other, but if (or when) the state attempts to foreclose its lien on the other co-tenant's interest, things could get messy, including the possibility of a forced sale (partition) of the property, which would require either that your mother buy the other 1/2 interest or accept half of the sale proceeds of the entire property, in which case she would have her money but lose her home. Other less drastic outcomes are also possible, but you need to show all the relevant documents to an attorney that practices real-estate law in your county and ask him or her to recommend defensive measures.