YouTube's  top creator, MrBeast,  is making a leap into fintech by buying a consumer banking app geared toward teens. His company, Beast Industries, is acquiring Step, according to a joint announcement sent Monday. Step, which describes itself as an "all-in-one" money app, is a digital banking platform designed to help young people get their financial start. The company offers a mix of services, including savings accounts, a credit-building Visa card that functions similarly to a debit card,