As a young boy, Swift took little interest in his studies and left the nearby country school after eight years. During that period he was employed in several jobs, finally finding full-time work in his elder brother Noble's butcher shop at the age of fourteen. Two years later, in 1855, he opened his own cattle and pork butchering business with the help of one of his uncles who gave him $400. Swift purchased livestock at the market in Brighton and drove them to Eastham, a ten-day journey. A shrewd businessman, he purportedly followed the somewhat common practice of denying his herds water during the last miles of the trip so that they would drink large quantities of liquid once they reached their final destination, effectively boosting their weights. Swift married Annie Maria Higgins of North Eastham in 1861. Annie gave birth to eleven children, nine of whom reached adulthood. In 1862, Swift and his new bride opened a small butcher shop and slaughterhouse. Seven years later Gustavus and Annie moved the family to Brighton (near Boston), where in 1872 Swift became partner in a new venture, "Hathaway and Swift". Swift and partner James A. Hathaway (a renowned Boston meat dealer) initially relocated the company to Albany, then almost immediately thereafter to Buffalo.