Is purgatory mentioned in the Bible? If not, when and where did it first get mentioned? What does the Bible actually say about life after death, as in what happens to us until judgement day?
Hi “treeleaf” The Catechism of the Catholic Church (CCC) says this, in regards to Purgatory.
(1030) All who die in God’s grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven.
(1031) The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. The Church formulated Her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. The tradition of the Church, by reference to certain texts of Scripture, speaks of a cleansing fire. (see 1 Corinthians 3:15; 1 Peter 1:7).
Hope this helps. God bless.
1 Cor. 3: Now if any one builds on the foundation with gold, silver, precious stones, wood, hay, straw –
 each man’s work will become manifest; for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each one has done.
 If the work which any man has built on the foundation survives, he will receive a reward.
 If any man’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire.
Mt. 5: Make friends quickly with your accuser, while you are going with him to court, lest your accuser hand you over to the judge, and the judge to the guard, and you be put in prison;
 truly, I say to you, you will never get out till you have paid the last penny.
Here’s a couple of biblical references. However, we Catholics are not “people of the book”. We don’t hold that the Bible is the sole rule of faith. The Bible is a part of Sacred Tradition, which also includes the oral teaching of the Apostles and the living Magisterium.
The word purgatory is not found in the Bible, but then neither is the word Trinity (nor is the full definition of the Trinity given), but we believe these things because they have been taught to us by the Church, which was founded by Jesus on Peter and the Apostles.
Others can give you more history of this teaching, but that should get the ball rolling.