I am adopting a family friends child. How can I go about getting financial support and subsidize rent.

Unless the child was in the foster care system, I doubt you do.

You don't get financial support and subsidized rent just for giving birth to a child, after all--why would you get it because you "have" a child another way?

If you can't afford to support the child WITHOUT subsidized rent and financial assistance, you probably won't be approved to adopt in the first place.