How do I file under-the-table farm work?

I have a friend who has been working as an under-the-table agricultural worker.  The grower pays cash and is also under the table and so there are no receipts or 1099s.  Normally people in this situation don't claim this kind of income but my friend is tired of not qualifying for loans because it looks like she makes nothing on paper.  Is it possible to claim this kind of income on her taxes?  She can say how much she made and can pay taxes on that money but there is no paper trail.  This isn't her only job.  She has a few other on-paper jobs.  

Thanks for your advice