Complex sentence: In the fall of 1829 he stumbled into his vocation as publisher and editor when--in order to save his family from destitution--he set up a printselling business with his brother-in-law, Gabriel Aubert.
Split into simpler sentences: In the fall of 1829 he became a publisher and editor in an effort to save his family from financial destitution. He set up a printselling business with his brother-in-law, Gabriel Aubert.