 Caldow attended Cumnock Academy and after leaving school became an apprentice painter with Cumnock Burgh Council.He started his football career with the local Glenpark Amateurs club, then Muirkirk of the Western Junior League.Caldow was signed by Rangers manager Bill Struth in 1952 and made his first team debut on 12 September 1953 in a 4–2 win over Ayr United at Ibrox.