How did McMurphy demonstarte that he was 'out of retirement'? What was he in 'retirement' from ?

Ratched likes to post financial information about the acutes. Most of the acutes have dwindling amounts of money where as McMurphy has more money than he came in with. This means McMurphy has been gambling and making money from the other patients and staff. The acutes joke that he can retire by the time he gets out.