<Sarcasm> I love the concept of half upfront. I like getting ripped off only half of the money instead of all of it. Makes me feel all warm inside. </Sarcasm>
Honestly, if I am ordering a multipage paper, say at least four pages, give me the first page for review without money upfront. If you really are a good writer, I am going to pay for the rest. Grab me in the beginning, and I will become a follower.
This being said, I tend to use the same people repeatedly once they have proven their value.