Consider what we've laid out so far. Considering the screens we've drawn and the fact that the owner was able to view and sign-off that this is what he wants, how many more questions are there to ask? Do we really need some excel document listing out requirements or a 30-page Functional Design Specification (FDS) document to tell you exactly what everything is supposed to be and do? Wouldn't this be enough? Does it have to really be done in Photoshop and produced as a slide deck?
Consider also that what we have done so far has cost us a grand total of five Post-it notes, one Sharpie, one pencil, and 20 minutes. I believe the case here has been abundantly made that for most sites, this is all you need and you can do it yourself.