as immmigrant, although you are entitled to apply for sunsidy for kids' daycare, it is still hard for you coz you need to study---normally daycare will be close by 5:30pm, every extra minute probably will cost you if you cannot take the kid, not mentioning the daycare spot and subsidy application needs a long wait
if you don't have a car, it is difficult esp in winter. language will not be a problem, u need to worryher Chinese. good luck
4yr old is relatively easy to get into day care.