It is 26th century. Technologies allowed everyone to have their basic income, but if a person wants to get something more, then it has to pick some place. Let's say, everyone comes with 1000cr to station. There may be some rates. For example, janitor's rate is 1.2; Librarian has rate of 1.2 as well; Clown and mime have rates of 1.0 . Engineering and Science have rates of 2.0, And so on...
Then, over some time delays, everyone gets something more (except civilians, since they have no assigned duties): rate * some basic value.
Credits should be used only for getting items from some vending machines (like now) or obtaining vanity or rare items (like champagne bottles, green cheese, checkered bags, golden jewelry, musical instruments).