Turnkey refers to something that is ready for immediate use, generally used in the sale or supply of goods or services. Turnkey is often used to describe a home built on the developer's land with the developer's financing ready for the customer to move in. If a contractor builds a "turnkey home" they frame the structure and finish the interior. Everything is completed down to the cabinets and carpet. "Turnkey" is commonly used in the construction industry, for instance, in which it refers to the bundling of materials and labor by sub-contractors. 'Turnkey' is also commonly used in motorsports to describe a car being sold with drivetrain (engine, transmission, etc.) to contrast with a vehicle sold without one so that other components may be re-used.
Similarly, this term may be used to advertise the sale of an established business, including all the equipment necessary to run it, or by a business-to-business supplier providing complete packages for business start-up. An example would be the creation of a "turnkey hospital" which would be building a complete medical center with installed high-tech medical equipment.