Dont have husband income proof how can i get maintanance .

I do domestic violence and maintanance case on my husband and inlaws in court. My husband doing business with my father inlaws at rental shop. They earn 5000-6000 daily. My husband not pay income tax. I dont have pfoof of his income. I am living with my parents with my 2 childerns. How can i proof his income in court . Is life style and expancec can be pfoof.