the documents required and visa fees for getting visa to visit Jiangyin

Kindly advice the documents required and visa fees for getting visa to visit Jiangyin, in order to inspect a merchant ship under our management and to sail with the vessel to her next port Ningbo. Since the exact date of arrival of vessel to her next port is not known can I take only the onward ticket to Jiangyin and then arrange the return ticket once I am ready to return??
There will be an agency for arranging my tickets and hotel accommodation in China.
What will be the maximum duration for which I will be eligible to get the visa.