Well I guess it depends on your definition of "turnkey" Loosely, it means buying a business that is ready to go. Basically put the key in the door and go.
But on the internet, turnkey can mean a website that someone else has built for you , content ready, seo ready and maybe even earning a couple dollars.
Turnkey can also mean all these cookie cutter sites that sell for pennies on the dollar.
MY opinion is if you purchase a "unique" turnkey business, you probably will succeed if you try. If you purchase one of the cookie cutter businesses, I doubt anyone will take you seriously.
Like I said - just my 2 cents
