I agree with Marko. We all need to work up to something, not to mention, if a customer tells Marko (for example) he wants a Carter made with 52100 steel and a handle made to a specific size, do you think Marko (or anyone) is going to turn him down? Hell no! There is far too much opportunity to say no. There's exposure, another notch in the belt, money (we all need it) and a chance to learn from one of the best.
A custom is anything made specifically for the customer, with that specific customer's preferences and desires in mind.