Need some information about documents to be submitted for L2 visa

Hello. My husband is appearing for his L1b blanket visa in chennai next month. According to his company’s policy I can apply for L2 only after his L1 is stamped. Meanwhile we were checking out the documents required and found out that I need to present 6 months bank statement of my husband at the time of my interview. My question is what is the purpose of checking the bank statement and what minimum balance should be maintained?