Stan Grossberg is Derek Shepherd's financial advisor. He assisted Derek, Callie, and the other doctors from the plane crash in buying the hospital.
Upon seeing that the hospital was going down when Pegasus wanted to buy it, Callie Torres proposed to the other doctors from the plane crash to buy the hospital themselves. However, none of the other doctors seemed willing to do so. When Derek was later talking to Alana Cahill about his face on the promotional material of the hospital, he overheard Owen saying to Bailey that he hadn't brought up the genome mapping treatment that Bailey wanted him to talk about to the board. This enraged Bailey and Derek realized the hospital couldn't go on like that.
He then decided to make a phone call to Stan, his financial advisor, saying he had a crazy idea and that he needed Stan to tell him how crazy it was. Stan discussed the legal realities of the situation with them. ("Hard Bargain")
Stan got the doctors a meeting with Julian Crest, whom he believed they could convince to give them the rest of the money they needed to buy the hospital. After meeting with a few of his interns, Stan got a call that they got a meeting with some higher-ups. In that meeting, they learned that Julian Crest was leaving for Dubai that evening, but he could make 15 minutes for them that afternoon. They met with him, but he ultimately decided not to invest the remaining amount they needed. ("This is Why We Fight")