In May 1833, with the assistance of friends interested in keeping him in New Salem, Lincoln secured an appointment from President Andrew Jackson as the postmaster of New Salem, a position he kept for three years. During this time, Lincoln earned between $150 and $175 as postmaster, hardly enough to be considered a full-time source of income. Another friend helped Lincoln obtain an appointment as an assistant to county surveyor John Calhoun, a Democratic political appointee. Lincoln had no experience at surveying, but he relied on borrowed copies of two works and was able to teach himself the practical application of surveying techniques as well as the trigonometric basis of the process. His income proved sufficient to meet his day-to-day expenses, but the notes from his partnership with Berry were coming due.