Leviticus 14:21 And if he be poor, and cannot get so much; then he shall take one lamb for a trespass offering to be waved, to make an atonement for him, and one tenth deal of fine flour mingled with oil for a meat offering, and a log of oil;
God didn’t limit salvation to you and what you could do! They were told what to bring as an offering. If they couldn’t bring that offering then there was always something that would show their faith in the Lord.
It was Him making a way for us! It is always God.