what type of social assistance are you referring to? Welfare or EI? I'm pretty sure if you are on welfare, he applies for a visa to visit you and says you are his source of financial support while there, it will be denied. I'm pretty sure CIC certainly does not like it when Canadians use welfare to support foreign visitors. Then again, i could be wrong, and they may not care if he can prove he's got enough money to support himself while there. The only way to know for sure is to actually apply and wait for a determination.
EI and Mat leave don't count as social assistance in the eyes of immigration. only welfare does.
