For startup brokers such as Robinhood and Webull, payment for order flow (PFOF) is the primary way of making money. With larger full-service brokers such as Fidelity and Schwab, the largest revenue source comes from sweeping the idle cash sitting in customer accounts into subsidiary banks each night. They also loan money to margin investors and charge incidental fees. Brokers also hope to upsell their commission-free stock investors into advisory services or other managed products.