CA real estate law, joint ownership in codo unit

In this situation, your mother arguably is entitled to reimbursement of 50% of all of the costs of upkeep, taxes, HOA Fees, etc. BUT, your father, as co-owner, arguably has a claim for 50% of the reasonable rental value of the property. That is, your mother is using the place when they could be renting it out to someone and splitting the proceeds. Since dad loses this opportunity due to mom's current use, he is arguably entitled to what he reasonably could expect to collect if mom wasn't using the place. If the reasonable rental value is greater than the $$ your mother has paid, then your mother may find that it is cheaper to remain mum on this subject.

David C. Beyersdorf