Obama is too young to retire. His career options are teaching, politics or being bored to death. IHis former Senate seat is held by a Republican, and is one of the key ones for a pickup by the Democrats. While only two presidents had real careers after leaving office (John Quincy Adams was an distinguished member of Congress, Taft was Chief Justice).
However there are press reports he’s shopping for an estate in Hawaii, though I expect his wife and kids see Hawaii as a nice place to visit but no more.