1910, originally theater slang for lower-salaried circuits, or ones requiring more daily performances; from noun phrase (also 1910). Compare big time.
Entries linking to small-time
big time n.
"upper reaches of a profession or pursuit," by 1909 in vaudeville slang. As an adjective by 1915. The same phrase was common in colloquial use late 19c.-early 20c. in a broad range of senses: "party, shindig, fun, frolic."