Legal analysis: the contract should be signed when the parties reach an agreement through oral consultation. Second-hand housing sales contracts should be the same. It is suggested that a complete written agreement should be signed first when conducting second-hand housing transactions, and all necessary contents should be clearly stipulated.

Legal basis: People's Republic of China (PRC) City Real Estate Management Law.

Article 36 When transferring or mortgaging real estate, the parties concerned shall register the ownership in accordance with the provisions of Chapter V of this Law.

Article 62 When a real estate is mortgaged, it shall be registered with the department specified by the local people's government at or above the county level. Where the land use right and house ownership are obtained due to the disposal of mortgaged real estate, the transfer registration shall be handled in accordance with the provisions of this chapter.