CA Civ Code Section 2985.1

A real property sales contract may not be transferred by the fee owner of the real property unless accompanied by a transfer of the real property which is the subject of the contract, and real property may not be transferred by the fee owner thereof unless accompanied by an assignment of the contract.

Nothing herein shall be deemed to prohibit the assignment or pledge of a real property sales contract, as security or for the purpose of effecting collection thereon, to the holder of a first lien on the real property which is the subject of the contract without a transfer of the real property or the transfer of a fee title in trust without the concurrent assignment of the sales contract.