Nobody has ever satisfactory explained where Epstein got all this money to begin with. He seems to have been running some sort of blackmail operation ensnaring wealthy people into criminal activity and videotaping them or otherwise recording it.
His first job was as a math teacher at a _girl's school_ run by the current Attorney General's father, and he seems to have leveraged that somehow into an investment job through one of the parents at the school, despite having no qualifications for that kind of work.
It seems worth noting that he went from working with young girls to sex trafficking them, and that the man who supposedly was going to get to the bottom of his murder is the son of the man who first gave him access to young girls.