Final answer:
A real estate broker must keep files regarding any real estate transaction for a specific period of time, typically five to seven years.
Step-by-step explanation:
A real estate broker must keep files regarding any real estate transaction for a specific period of time. The duration of this period may vary depending on local laws and regulations, but a common timeframe is five to seven years. During this time, the broker should retain documents such as purchase and sale agreements, financial records, property disclosures, and any relevant correspondence.