Is it permissible for me — as I am poor — to give my son up for adoption in exchange for money?

Adoption is forbidden in Islamic law. It is not permissible to allow your son to be adopted, whether for financial compensation or without it. Accepting financial compensation is a greater sin and resembles selling a free person. If someone wishes to care for your son and show kindness to him, from those who can be trusted with him, there is no harm in that, without adopting him, provided that the son is not harmed.