When does one become Regenerated? Does it happen before in order to empower us to believe or does it happen after we believe?
Play nice
The answer to your question is, a Believer becomes Regenerated after he Believes.
We see the first mention of the need for and the process of Regeneration form Jesus in His discourse with Nicodemus.
John 3:1-8
1) There was a man of the Pharisees, named Nicodemus, a ruler of the Jews:
2) The same came to Jesus by night, and said unto him, Rabbi, we know that thou art a teacher come from God: for no man can do these miracles that thou doest, except God be with him.
3) Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
4) Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?
5) Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
6) That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
7) Marvel not that I said unto thee, Ye must be born again.
8) The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit.
We see that Nicodemus professed his BELIEF, to Jesus.
Jesus answered him by telling him he must be Barn Again in order for him to be able to SEE The Kingdom of God.
Nicodemus did not understand how he could be Born Again a second time
Jesus then tells Nicodemus for the second time he must be Born Again in order for him to ENTER The Kingdom of God, explaining to him that, there is a realm of the Flesh which he lived in, and the realm of the Spirit where the Kingdom of God exists, which is the place where God dwells.
The process Jesus explains for this transformation to take place is through Baptism, being Born Again both in the Water and the Spirit.
Jesus then went on in his explanation saying, when a human being is born, he lives in the Realm of the Flesh, but the human which becomes Born of the Spirit, now resides (ENTERS) in/to the Spiritual Realm, which is The Kingdom of God.
This therefore is when the Regeneration of the Human, (Believer) actually takes place.
How then do we know this is so?
From the words of Jesus Himself, both above where he referenced Regeneration to Nicodemus, and below where He gave the Great Commission to the Apostles, describing not only Believing but the Regeneration process which is necessary for the Believer, placing them in the order of not only their occurrence, but the order when a Believer does truly become Regenerated by the Holy Spirit.
Mar 16:15,16
15) And he said unto them, Go ye into all the world, and preach the gospel to every creature.
16)
He that believeth and is baptized shall be saved; but he that believeth not shall be damned.
Now in answer to your question, the place where the word Regeneration is used to explain When, Where, How this process actually does take place is found in Jesus own words.
1) Except a man be
born of water and of the Spirit, he cannot enter into the kingdom of God.
2) Except a man be
born again, he cannot see the kingdom of God.
BORN:
G1080
γεννάω
gennaō
ghen-nah'-o
From a variation of G1085;
to procreate (properly of the father, but by extension of the mother);
figuratively to regenerate: - bear,
beget, be born, bring forth, conceive, be delivered of, gender, make, spring.
G1085
γένος
genos
ghen'-os
From G1096; “kin” (abstractly or concretely, literally or figuratively, individually or collectively): -
born, country (-man), diversity, generation, kind (-red), nation,
offspring, stock.
G1096
γίνομαι
ginomai
ghin'-om-ahee
A prolonged and middle form of a primary verb;
to cause to be (“gen” -erate), that is, (reflexively) to become (come into being), used with great latitude (literally, figuratively, intensively, etc.): - arise be assembled, be (come, -fall, -have self), be brought (to pass), (be) come (to pass), continue, be divided, be done, draw, be ended, fall, be finished, follow, be found, be fulfilled, + God forbid, grow, happen, have, be kept, be made, be married, be ordained to be, partake, pass, be performed, be published, require, seem, be showed, X soon as it was, sound, be taken, be turned, use, wax, will, would, be wrought.
The process of Regeneration
Rom 6:4-7
4)
Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father,
even so we also should walk in newness of life.
5) For if we have been planted together in the likeness of his death,
we shall be also in the likeness of his resurrection:
6) Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
7) For he that is dead is freed from sin.