Teach A Cat

I just found a baby mouse i need help to take care of it. my cat bite it but it is still living we put proxside of the wound .it is feeling better and it is moving. know i need to know how to take care of it its eyes is sometime open but mostley cloused what do i feed it?
somtimes it opens it mouth and makes a weard sound.
can they drink water?

My husband and I have never had a pet before. How much is the monthly expense to properly care for a cat?