From the Super Mario Wiki
Boodin is a resident of Flopside in Super Paper Mario. Like his Flipside-counterpart Hoodin, Boodin owns a Catch Card store know as Fondest Hopes. He is found always in his shop, selling Caught Cards and Catch Card SPs to Mario, Princess Peach, Bowser, and Luigi.
He seems very fond of card games with his costumers, as stated by Tippi: "He likes to hang out with the weekend adult costumers. He likes to play cards more then he collects them."