Usage examples "gainful":
Nursing, as a gainful
calling, a hundred years ago was a mercenary affair into which undesirable people went for what they could get out of it. - "Christianity and Progress",
Harry Emerson Fosdick.
The fine days he professed to regard with keen suspicion as weather breeders, when it was imprudent to go far from home, especially in the direction of the Crenshaw timber lands, which for years had been the scene of all his gainful
industry, and where he seemed to think nature ready to assume her most sinister aspect. - "The Prodigal Judge",
Mr. Cavendish, accepting the judge's ultimatum as something which must debar Hicks from all further consideration, and being, as he was, exceedingly active and energetic by nature, if one passed over the various forms of gainful
industry, uttered a loud whoop and threw himself on the overseer. - "The Prodigal Judge",