There’s some clever wordplay here, Common is a very conscious rapper who regards Afrocentricity highly. Following on from the previous line, Common wants a change from the racism and prejudice on African Americans.
Common also refers to his friend who wants change, but this is a different kind of change, Common’s friend who is likely homeless is asking for spare change (small amounts of money usually pennies, dimes etc.) from people. Homeless people who beg for money are usually seen carrying their money in cups.

He calls the ghost Casper which is a reference to Casper the friendly ghost