I'm sure that Fogg knows how he made his own fortune (or inherited it); however, Fogg, the narrator, or a different character never explains to readers exactly how he became so wealthy. Fogg is a member of the British aristocracy. He's a wealthy gentleman that appears to have nothing but time on his hands and things to spend money on. That is the general appearance and stereotype of this class, and audiences are often given the impression that someone like Fogg is wealthy and always has been wealthy. He could very well have been born into the money. Often, this kind of thing creates a character that is not likable or relatable; however, that is not the case with Fogg. He doesn't flaunt his wealth by buying and doing frivolous things. He's fairly humble in general, and he's humble about his wealth. That said, he's not afraid to use large sums of money for a cause or a purpose. That is especially true when it comes to helping out a friend such as Passepartout.