Here where I live, we call it deposit. Can we pay it if artist/agent does require it? Yes, we can.
Is usually agent asking for deposit? Not all the time.
As you said, agent is here for controlling the things to be safe for artists, no matter money or security wise, how come they are not asking for the deposit regularly, let say 50%???
Sry mate, but you are absolutly missing the point of this debate.