Turn-Key, the "n" was dropped, or it is simply more of Grinner's special way of saying/writing. Bein' from Taxes an ALL thet. ;-)
I'm pretty sure you know what what turn-key is.
Grinner's spot on with your concerns. I go flat fee and hourly, but after 20 years in the business, and figuring for all the stuff a client is capable of throwing at you during the process, I've gotten fairly accurate in my bids for flat fee, based on the hours I think it will take.
In fact, most of my clients would come out with a smaller bill if they went hourly because I build a LOT of contingencies into my flat bids - just in case, and add another 10 percent on top of that.