Actually, if you get a container load of goods you pay demurrage on the container itself. It belongs to the shipping company and they rent it to you, it is not yours to keep.
As mentioned above, they can be purchased, but I don't think that was your question.
Generally you have 24 hours to unload it, anything more and you pay for the time. You will also pay for the drayage fee for bringing the contaier to you.
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