Complex sentence: Marriage was impractical, as both Lefroy and Austen must have known; neither had any money, and he was dependent on a great-uncle in Ireland to finance his education and establish his legal career.
Split into simpler sentences: Marriage was impractical, as both Lefroy and Austen must have known. Neither had any money, and he was dependent on a great-uncle in Ireland to finance his education and establish his legal career.