Thank you. Do they get financial aid to help support their families?
Your original question asked how to they do it if they are not on welfare.
If they don't need finanacial aid, they don't ask for, or get financial aid.
If they have a lot of children, they get taxed at a lower rate because each child they support is an exemption. In 2011, they can deduct $3700 off their income for each child.
I don't know if you consider that financial, or what your definition of financial aid is.
They can also apply for scholarships, etc.