The Illinois Real Estate License Act requires licensees to provide agency disclosure:

Agency disclosure is a fundamental requirement in real estate transactions that protects both consumers and licensees. This question tests knowledge of when Illinois licensees must provide agency disclosure, which is crucial for establishing the legal relationship between agent and client. The correct answer is B because Illinois law specifically requires disclosure at first substantive contact - this is when the licensee begins discussing specific property information or a client's particular needs. This timing ensures transparency early in the process, preventing potential conflicts of interest. Option A is incorrect because waiting until closing is too late - the relationship must be established before negotiations begin. Option C is wrong because disclosure is mandatory, not optional. Option D is incorrect because disclosure is required for both buyers and sellers. This question challenges students by testing their knowledge of specific timing requirements rather than just the general concept of agency disclosure.