Walt’s motivation isn't really money; it’s agency. He is a man who has been "emasculated" by the modern world (underpaid teacher, passive husband, terminally ill patient). Cooking meth gives him power. The sex scene in the pilot where Walt attacks Skyler is uncomfortable because it highlights his toxic shift.
If you have the Blu-ray box set, the Season 1 disc includes deleted scenes (including an extended dinner conversation at the Schrader’s house) and a behind-the-scenes featurette: "Making Dirt: The Chemistry of Breaking Bad."