Q.At which rank or CoC level is it recommended to pursue ship broking roles ashore?

Ship Broker is completely different profile from the sailing staff. Most of the ship brokers may never have sailed on a ship. The key skill required for a ship broker is the ability to negotiate and relationship building skills.

Having said that, basic knowledge of ships and how the ships operate definately help when choosing to be a ship broker. Advanced knowledge of ships and ship handling is generally not required.

So for seafarers looking for a job as a ship broker should ideally switch after sailing as 3rd mate or 2nd mate.