He is at the point that his brother can't keep up with him and in the further future, the struggle of climbing rank and taking/defending title might happen. Also, I believe that some of shogi players do have side job since sometimes the board doesn't pay you well.
Is wooden board game really worth to bet with?
Unless you're a natural like Magnus, I don't think it is a good idea. He is already struggling in a rank where the geniuses struggle and eating each other. Even if he climbed the rank, he will facing greater giants. But yeah, i'm not an athlete so...