Cal. Civil Code § 2794

A promise to answer for the obligation of another, in any of the following cases, is deemed an original obligation of the promisor, and need not be in writing: (1) Where the promise is made by one who has received property of another upon an undertaking to apply it pursuant to such promise; or by one who has received a discharge from an obligation in whole or in part, in consideration of such promise; (2) Where the creditor parts with value, or enters into an obligation, in consideration of the obligation in respect to which the promise is made, in terms or under circumstances such as to render the party making the promise the principal debtor and the person in whose behalf it is made, his surety; (3) Where the promise, being for an antecedent obligation of another, is made upon the consideration that the party receiving it cancels the antecedent obligation, accepting the new promise as a substitute therefor; or upon the consideration that the party receiving it releases the property of another from a levy, or his person from imprisonment under an execution on a judgment obtained upon the antecedent obligation; (4) Where the promise is upon a consideration beneficial to the promisor, whether moving from either party to the antecedent obligation, or from another person; (5) Where a factor undertakes, for a commission, to sell merchandise and act as surety in connection with the sale; (6) Where the holder of an instrument for the payment of money, upon which a third person is or may become liable to him, transfers it in payment of a precedent debt of his own, or for a new consideration, and in connection with such transfer enters into a promise respecting such instrument.