Both of you will be required to produce income information at the hearing which will include your income tax returns, W-2 forms and pay stubs. There is an expense form that is also generated for the hearing, but some courts do not look at it unless there is an unusual or extraordinary fixed monthly expense. Outside of those documents, may be able file for formal discovery by serving him with a list of documents that he must produce within 30 days. However, you must first designate your case as complex in order to engage in discovery. You should speak with an attorney to discuss this matter.
My response is based solely on the limited information contained in the question. It is not meant to substitute your attorney's advice.
In most jurisdictions you are required to have permission from the Court to seek discovery from the other party in support matters. However, you are both required to provide that information to the Court at the time of your hearing. If he is a business owner it is not uncommon to have 'income' that is not disclosed in a traditional way. You should be able to submit a discovery request to try and discover all of his earnings.