OK, I think I have answered (in green below) most of my own questions by downloading the trial version and spending a few hours with it. But I could still use any help with the ones in red below!

1) When you buy Synthesizer V Studio Pro do you get any of the voices or must you buy at least one voice database?
Looks like you do NOT get much except lite versions that cannot be used in published projects so I'll need to buy at least one vocal database.

2) If you get a "starter set", do you get enough to do anything useful?
Answered above.

3) Are the vocals stored similarly to RealTracks in snippets of analog audio files?
Looks like they are not complete words or phrases, instead, they are phonemes which provides a LOT more flexibility.

4) Are the individual words sung, recorded and stored, then used to assemble the vocals?
Answered above.

5) If #4 is true is there any limitation on the number of different words each vocalist can sing in your song?
Answered above.

6) Is there one male vocalist and one female vocalist that would be considered general purpose country/folk/pop? (That cover of Desperado with Hayden sounded pretty good!)
Still need help on this one.

7) Are there limits on what key each singer can sing in?
Still need help on this one.

8) Can you use fx on the vocals such as the presets of izotope Nectar and do these cause artifacts or other issues?
I did a quick demo of Mary Had A Little Lamb and it exported perfectly and accepted Nectar presets with no degradation that I could detect..

9) Does the license you purchase allow you to distribute and sell your songs without any special licensing or royalties?
Looks like you can publish/sell your work if you purchased the license to the software and the vocal database you wish to use.

10) Do they typically do Black Friday sales? The current deal I am considering is Synthesizer V Studio Pro + Any Voice Database Bundle for $161
Still need help on this one.