Texas Real Estate Commission rules state that you must know the local market where you provide services to a client. The relevant section of TREC §531.3: Competency states:

It is the obligation of a license holder to be knowledgeable and competent as a real estate brokerage practitioner. The license holder must:

  1. be informed on local market issues and conditions affecting real estate in the geographic area where a license holder provides services to a client.

To stay in compliance with the rule, avoid working with clients in areas where you are not knowledgeable.