Legal Question in Real Estate Law in California

Yes, indeed, there MAY be a way for A to assert that he/she is a partial (or even 100%!) owner and, as such, to be exempt from eviction. Your question does not provide enough facts to ascertain whether a so-called "purchase-money resulting trust" arose at the time the $15,000 investment was provided, nor what other funds, if any, were used for the down payment. However, there is a legal principle that ownership of real property follows the source of the cash money used to make the down payment.

If you would like a more detailed analysis (free) as to whether A can prevail against B and have a court declare A to be at least a partial owner of the property, please contact me directly with particulars as to how the $15,000 was raised, delivered and used in connection with the house purchase. I would need to know what other funds were used as down-payment, and full details as to any oral or written understandings between A and B as to what the $15,000 was to be used for and with what ultimate result intended.

Purchase-money resulting trust cases are not a slam dunk to plead and prove, and many judges are unaware of the principle. However, it is a way for someone who put up part or all of the purchase price for real estate, but got a smaller (or none) of the legal title, to have a court order correction of record title to reflect the same ownership as the contribution(s) to the down payment would indicate.