How to prove our income to sponsor our parents?

Hi all, hope you have a good day.
My husband and I would like to sponsor my parents to Canada, we are co-signors. Our 2009 income is just above the cut-off standard, but what I concern is that some of our income sources were from verbal agreement with cheque payment. In another words, I got and finished projects from a private company (it's not steady, the project is not always available), and then they paid me a sum of money in cheque with their company letter head on the cheque. My question here is that can I include this source of income in our application?
Many thanks in advance.

You will need to file taxes as a proprietor or small unincorporated business operator.  This can be done on the standard tax forms, but you have to produce a statement of income and expenses for your business activities.  As long as you declare the income and pay your taxes, it certainly counts! (If you declare it and don't pay the taxes, it will show on your Option C and you may be rejected as a sponsor.)