Nearly all have some idea or ideas. Some make it clear that they're not wedded to their idea, which is fine with us, actually.
I quit my job three months ago and have been doing consulting work in order to generate enough runway to finally dedicate ourselves fully to our own product.
I think we will be done with all of our current gigs by november, so the Winter YC cycle looks VERY attractive right now. We have a couple of ideas, and it seems like we might have enough time to get started on them before YC, but still be flexible enough when the cycle starts.