This guide covers staffing agencies, day labor, and joint employment from the tests that determine which entity is an employer for which statute through wage liability, safety, workers' compensation, discrimination, contracting, and audit. It explains why joint employment has no general answer — the same two companies can be joint employers under one law and not another for the identical relationship — and sets out the economic reality, common-law agency, and labor relations approaches with the statutes each governs. It treats client wage liability as the most common and least expected exposure, works through the timekeeping and regular-rate failures specific to staffing, and identifies the State statutes making client liability express. It sets out the safety allocation between agency and host, the multi-employer worksite doctrine, and the training gap that produces most citations. It explains the borrowed servant doctrine that usually bars an injured temp's suit against the client that hurt them, and where it breaks down. Separate parts address day labor, professional employer organizations, temp-to-hire conversion fees, no-poach antitrust exposure, screening and verification allocation, the staffing agreement, and audit programs for both sides.