Social Assistance/Ontario Works is effectively ZERO income. If the person drawing it is CAPABLE of working, you can try and have an income imputed equal to full time hours at minimum wage.
BUT...drawing assistance is seen as zero income in the eyes of the court, at least according to my QC rated, $400 an hour lawyer with over 30 years of experience.
(I think it has more to do with the amount received by the individual person being so low as to be UNDER the minimum standards for CS to be paid, but at the end of the day, it doesn't matter WHY. If the capability is there, there are avenues you can take (vis a vis imputing income). )
I was in a similar boat with my ex...and still am...she prefers to sit on assistance and do nothing to contribute to the kids. Lawyer advised me to save my money, since it's akin to getting blood from a stone.
EDIT: EI counts as income, since it directly affects your line 150 amounts.