Fifty percent upon booking, payable in cash, fifty percent on arrival, payable in cash is what I would consider necessary. My fee would not cover flights, meals or anything else, as they are the clients expenses. I would also need to do a security check unlike a normal booking, I would want a place of work and at least one other form of identification. Sounds harsh, but there we go.
[Psst you pressed "quote" instead of "modify". Edited to fix. - Anika]