If a new mother could not afford a lamb for her purification, what could she bring?

Answer: Two turtledoves or pigeons

Leviticus 12:8 allowed two turtledoves or two young pigeons, one for a burnt offering and one for a sin offering.

“But if she cannot afford a lamb, she shall bring two turtledoves or two young pigeons, one for a burnt offering and the other for a sin offering. Then the priest will make atonement for her, and she will be clean.’””— Leviticus 12:8 (BSB)