Legal analysis: I entrust in writing, which is valid. 1, the purchase contract generally needs to be signed by the purchaser for confirmation, which is a citizen's right. Because the contract law stipulates that the contract will take effect after being signed by both parties. 2. If the purchaser is unable to sign due to special circumstances, he may entrust other adult citizens to sign and seal in writing. 3. As long as there is a written authorization from the buyer, it is valid for the agent to sign on behalf of the buyer.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 209 The establishment, alteration, transfer and extinction of the real right of immovable property shall take effect after being registered according to law; Without registration, it will not take effect, except as otherwise provided by law.

Article 920 The principal may entrust the agent to handle one or more specific affairs, or may entrust the agent to handle all general affairs.

Article 922 The agent shall handle the entrusted affairs in accordance with the instructions of the principal. If it is necessary to change the client's instructions, it shall be approved by the client; If it is difficult to get in touch with the client due to an emergency, the agent shall properly handle the entrusted affairs, but shall report the situation to the client in time afterwards.