Psych (detective agency) is the private psychic detective agency Shawn began with Gus in the Pilot episode. Their business does receive clients, but it's unknown whether or not there have been other clients than those mentioned in episodes. Shawn started and named the agency without Gus's knowing, and called it Psych, saying the best way to make people believe you is to tell them that you're lying to them. He used Gus's credit card and forged his signature on the lease. The Psych office is like a second home to both Shawn and Gus with it's own bathroom, kitchen, and entertainment system.
Shawn and Gus do recieve clients through their psychic detective agency but the bulk of the investigations come from involment with the Santa Barbara Police Department. The Psych detective agency also tends to reveal past cases which wrongly incarcerated people or closed due to lack of evidence.