Money works as in any large city. You come in with the money of your
place of origin (assuming you haven't made adjustments prior to arriving),
and exchange it for prevalent Earth value credits, as determined by the
current exchange rate. You are issued a credit chit that has your name,
ID, other information, including genetic information to prevent forgery,
and that has your available credits as stored in the B5 computer. As you
pay, as with any credit card, you whittle away at that amount until it's
gone, at which point you either cash in more of your money...or go broke.

jms