Marine Transport Inc. - Hauling Containers

I am thinking about going to work as a subcontractor for someone who will be pulling containers for Marine Transport Inc. Has anyone worked there? I have hauled cars, but never containers, so I have a little port experience. I will be going to Savannah and or Charleston, and I will be out of Atlanta. I know that they have facilities in all of these cities.

Does anyone know if I will actually have to enter the ports? Are there facilities in the port, or external? I had a JAXPORT credential, but had to turn it in after I left that job, and I had a little trouble getting it, due to a pending situation, which is still pending. Will I have to get a GA ports Authority and SC card AND a TWIC card, or just one or the other? If I can just go to their terminal and drop and hook, that would be perfect for me. I am hoping to avoid the ports if possible. Is this a realistic expectation? Do they have yard dogs that just drive the containers in?

What is a reasonable expectation as far as pay? I am guessing percentage. He is running under their authority, and I am being employed by him as a sub-contractor. Should I expect the percentage be from the total revenue from the load, or calculated from his cut? In other words, if the load pays $1,000, should I expect say $250 from that load, or should I expect 25% of his percentage, say 80%. 80% of $1,000 would be $800, and 25% of that would be $200. I have worked for this guy before, and he does not like to pay very well, so I am wondering going in what is normal range.

Any and all advice would be greatly appreciated, as I do not know anything at all about containers.