Whoa! Thems there a whole heap-o-questions!
Ok, here's my personal take, one at a time:
1) Dry or Produced
My vote is almost always Dry. I prefer to work with clients that have their own production, and as you said, pros will want to hear my un-altered voice...
2)
VO Theft
I don't use watermarks because I find them annoying and they show a lack of trust on our part. I have changed the copy as James suggested (different phone or web site). I like that option the best, but only when it's a potentially questionable client. Most on V123 are hidden, so they're all questionable for me. Voices.com at least tells you something so you can research up front (kudos to them ;-)
3) Payment
For large projects or questionable clients, I'll ask for payment (half or full) up front, and the balance on delivery. Sometimes I will send a low quality audio for approval, then send the final once they've paid. However, I do many of my jobs with delivery up front, payment due after delivery. So far most have paid up (sometimes it takes a while, tho...)
Oh, and I don't do the extra fee for late payment. Just a personal preference.
So, there it is then...,
Joe J Thomas
www.JoeActor.com