Complex sentence: He established a good relationship with Mr. Hampton, as indicated by the numerous formal contracts they entered into over a ten year time span; during which he used his earnings to purchase the freedom of his wife and children, and add to his land holdings.
Split into simpler sentences: He established a good relationship with Mr. Hampton, as indicated by the numerous formal contracts they entered into over a ten year time span. During this period, he used his earnings to purchase the freedom of his wife and children, and to add to his land holdings.