Which of the following types of knowledge should be kept confidential according to law?

The confidentiality of a previous or current occupant's HIV status is protected by law due to federal and state privacy and discrimination laws. Specifically, the Health Insurance Portability and Accountability Act (HIPAA) provides strict guidelines on the protection of individuals' health information, which includes HIV status. Disclosure of such personal health information can lead to discrimination, stigma, and violation of privacy rights. As a result, real estate professionals are legally obligated to keep this information confidential and cannot disclose it without explicit consent from the individual concerned.

In contrast, the other options involve information that does not carry the same level of legal protection. An occupant's previous job is generally considered non-sensitive and does not have confidentiality guidelines governing its disclosure. The property owner's financial status, while sensitive from a personal perspective, is not protected to the same extent legally, particularly in real estate transactions where financial disclosures can be relevant. Lastly, neighborhood crime statistics are public information and do not fall under the category of confidential information, as they are often readily available to the public and can be shared without legal repercussions.