Solon, long before Caesar was ever born in Rome, abolished debt-slavery in Athens.
There's a good book on Athenian banking:
Cohen, E. 1992. Athenian Economy and Society: A Banking Perspective. Princeton, NJ: Princeton University Press.
He goes into interesting evidence for bank money (ledger entries not backed by coins, as opposed to metal currency), fractional reserve lending, and inflation in ancient Athens.
It turns out one of the largest banks in Athens was owned/run by some slaves: finance was not a 'respectable' profession—with farming/agriculture being the most 'noble'—so it was left to the lower classes and other riff-raff. Lots of slaves ran businesses, and the question often came up whether any associated debt belong to the business, the slave, or the slave's master (important when slaves were bought and sold).
There's a good book on Athenian banking:
Cohen, E. 1992. Athenian Economy and Society: A Banking Perspective. Princeton, NJ: Princeton University Press.
He goes into interesting evidence for bank money (ledger entries not backed by coins, as opposed to metal currency), fractional reserve lending, and inflation in ancient Athens.