What are the legal requirements to buy an apartment?

The verified evidence provided exclusively covers the Chinese sitcom 'iPartment' (Chinese: 爱情公寓), its production details, seasons, and a 2018 film adaptation. This evidence contains no information regarding real estate transactions, apartment purchases, or any legal requirements associated with buying property. Since my guidelines require grounding answers strictly in the provided evidence, I cannot access or reference external knowledge about real estate laws to address this question.