This term came about in the building industry primarily when a contractor built a custom home from start to finish and handed over the keys to the new homeowner upon completion. Today it may be the entire project or just a single phase, like framing a house or installing the windows. Many products can be purchased and installed Turnkey. So you don't have to hire several subs, pay multiple vendors and schedule the work to be done yourself.

Maybe your next project, is a turnkey project.