Buying black market organs is a sin. Not only are you stealing another person's kidney or liver, but the mere fact that you even thought about coveting another man's body part is a sin.
It doesn't matter that you may die without it or that it is the doctor performing the surgery who murdered the man they took the body part from, you are still stealing another man's body part to extend your own life.
That is disgusting, shameful and un-Christian.
If your health is failing you it means God is punishing you for losing your faith. You must pray to God and restore your faith for you to be healed by the miracle of the Lord's power.
Praise Jesus!