Legal Question in Real Estate Law in California

You could initiate a partition action -- but if filing the suit didn't result in your sister caving in and selling right away, and the suit worked its way through the court system, I doubt that you'd get your money much faster, and you'd probably get less net proceeds, due to the costs of suit. Also, suits among family members create hard feelings (although they may already exist here).

Oops, sorry, I just realized that you make it plain that you don't have a present ownership interest ....... therefore, you could not initiate a partition action! My mistake. Your only hope would be to convince the other co-owner to initiate the action. However, I don't recommend partition in your situation because it is slow and costly. Maybe someone would purchase your note? Or would the sister give you an advance part-payment?

Have you considered selling your note?

You apparently sold you ownership interest in the property, and have no more 'say' in what is done with it. You can try to collect on your note, or you can 'factor' or sell your note at a discount to get quick money. First try to get one of the sisters to pay you off, or buy your note, even if at a discount.