Money talks in The Big Sleep. Well, not literally. But if you have a lot of money in this novel that pretty much guarantees you all the power and influence you want. The Sternwood family is the epitome of the wealth = power equation: their money comes from oil wells, and various members of the family succeed in using this wealth to buy what they want. But money also corrupts. And that's is why Marlowe not only despises the filthy rich, but also prefers being poor and underpaid if it means he doesn't have to compromise on his own morals.
It's all about the benjamins, baby. Money is the driving force behind the criminal activities throughout the novel, from the blackmailing schemes to the various murders.
Marlowe attempts to preserve his own integrity and honesty by living modestly, yet he still finds himself somewhat attracted to the life of the rich.