In Louisiana, you have to show that parental custody will cause substantial harm to the child. This means something very serious, like abuse, violence, abandonment or neglect.
A parent's low income is not enough to deny her custody. That the child wants to live with you instead of a parent is also not enough.
You also have to show that living with you would be good for the child. It is not easy to win custody from a parent. You should get a lawyer.