In 1907, at the age of 18, Walker was apprenticed to Providence architect Howard K. Hilton. The three-year apprenticeship paid one dollar a week for the first year, two a week for the second year and three a week for the third. While working there Walker attended classes at the Massachusetts Institute of Technology. After two years had moved up to a design position, paying nine dollars a week. He left during his final semester before graduating, and, in 1913, married Stella Forbes, of Providence. He was a Rotch Traveling Scholar in 1916.