During his career, Holmes works for the most powerful monarchs and governments of Europe (including his own), wealthy aristocrats and industrialists, and impoverished pawnbrokers and governesses. Although when the stories begin Holmes initially needed Watson to share the rent for their residence at 221B Baker Street, by the time of "The Final Problem", he says that his services to the government of France and the royal house of Scandinavia had left him with enough money to retire comfortably.

The detective tells Watson, in "A Case of Identity", about a gold snuff box received from the King of Bohemia after "A Scandal in Bohemia" and about a valuable ring given to him by the Dutch royal family; in "The Adventure of the Bruce-Partington Plans", he receives an emerald tie pin from Queen Victoria. In "The Adventure of the Priory School", Holmes rubs his hands with glee when the Duke of Holdernesse mentions his ₤6,000 fee, the amount of which surprises even Watson (at a time where annual expenses for a rising young professional were in the area of ₤500). However, in "The Adventure of Black Peter", Watson notes that Holmes would refuse to help even the wealthy and powerful if their cases did not interest him.