WHAT HAPPENS NEXT?
Just to give you a rough idea of how Blish cities will work, when you are satisfied with the city's size you will fit the city out for the economic level it will operate at (agri, resource, etc - but not bio). This fitting out will take another few days before you can finally launch the city into space. You then direct it to a planet in the cartel's hub system or in another cartel star system. It will take time for the city to get there because they move very slowly, being huge installations with not very powerful engines.
Once it arrives at its destination, the owner of the host star system takes control and can specify what commodity it should produce, and for which planet in the system. Each production slot can be set for a commodity, and you can have more than one slot churning out the same commodity if you like.
The amount that each production slot produces will be random, determined when the commodity is set. The commodities are not fixed, and you can change the commodity a slot produces, although this re-tooling will take time to complete, during which time the production slot won't be operational. You can't change the economic level once the city has been built.
One big advantage of Blish cities is that the production doesn't use up any planetary resources. A star system can only have one city it in at time, though, because the resources it gets from asteroids and so on will only support one city at a time.
The cartel owner will be able to move the city to another planet in the star system, or to a different system, which of course will take time. The PO will also be able to eject the city if it becomes unwanted, in which case it will return to its home base in the hub system.