Houses in heaven or believers abiding with God in Christ?

In My Father’s house are many mansions; if it were not so, I would have told you. I go to prepare a place for you.
-John 14:2 (NKJV)

John 14 is commonly understood and preached as an encouragement that houses in heaven built by Jesus await believers.  But this is not what he was talking about.  The message of the Gospel of John is that Jesus came to give us life, eternal life that begins now when we believe.  The gospel message is not "believe so that you can go to heaven when you die", but rather "believe and enter in to life in Christ now and forever".  Heaven is not mentioned much in the Bible.  Living obediently towards God and as a disciple of Christ today is the message of the Bible.

John 14:2 must be understood in the context of John 14 and 15.  Jesus is teaching about recieving life through abiding:

At that day you will know that I am in My Father, and you in Me, and I in you.

-John 14:20

Jesus answered and said to him, “If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him.

-John 14:23

Abide in Me, and I in you. As the branch cannot bear fruit of itself, unless it abides in the vine, neither can you, unless you abide in Me.

“I am the vine, you are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing. If anyone does not abide in Me, he is cast out as a branch and is withered; and they gather them and throw them into the fire, and they are burned. If you abide in Me, and My words abide in you, you will ask what you desire, and it shall be done for you.

-John 15:4-7

The Father abides (dwells) in Jesus:

 Do you not believe that I am in the Father, and the Father in Me? The words that I speak to you I do not speak on My own authority; but the Father who dwells in Me does the works. 

-John 14:10

The Holy Spirit abides (resides) in believers:

the Spirit of truth, whom the world cannot receive, because it neither sees Him nor knows Him; but you know Him, for He dwells with you and will be in you. 

-John 14:17

Before he died, rose, and ascended; Jesus abided (was present) with his disciples:

“These things I have spoken to you while being present with you.

-John 14:25

The dwelling places, the 'mansions' (KJV, NKJV) prepared for believers that Jesus spoke of in John 14:2 are simply abiding in Him!

Jesus finally ends his teaching about how to live now that he will be gone with a prayer in John 17 that caps off and emphasizes this same point of believers living today on earth abiding in Him and The Father:

“I do not pray for these alone, but also for those who will believe in Me through their word; that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me. And the glory which You gave Me I have given them, that they may be one just as We are one: I in them, and You in Me; that they may be made perfect in one, and that the world may know that You have sent Me, and have loved them as You have loved Me.

-John 17:20-23

Jesus has been encouraging his disciples about how to live their lives on earth.

John 14:2-4 is not about heaven, but is part of a discourse from Jesus about how to live in Christ on earth before we die.

The context tells us what the text means.  Let's switch now to the CSB:

Don’t let your heart be troubled. Believe in God; believe also in me. In my Father’s house are many rooms. If it were not so, would I have told you that I am going to prepare a place for you? If I go away and prepare a place for you, I will come again and take you to myself, so that where I am you may be also. 

-John 14:1-3

Jesus answered, “If anyone loves me, he will keep my word. My Father will love him, and we will come to him and make our home with him.

-John 14:23

The "many rooms" in the Father's house are the "home" God makes in every believer.

In my Father’s house are many rooms. If it were not so, would I have told you that I am going to prepare a place for you? If I go away and prepare a place for you, I will come again and take you to myself, so that where I am you may be also. 

-John 14:2-3

Nevertheless, I am telling you the truth. It is for your benefit that I go away, because if I don’t go away the Counselor will not come to you. If I go, I will send him to you.

-John 16:7

Jesus goes away, but sends the Counselor.  Jesus' going results in the Spirit coming.  This is all about life on earth which is the beginning of eternal life.  Jesus' body being removed resulted in the Spirit coming and the age we live in now of Jesus being in heaven with the Father while the Spirit is one earth in believers which is authentic or normal Christianity.

John 14-17 are rich teachings from Jesus about living out life in Christ on earth.

Believers now are the body of Christ, the Father's house:

Don’t you yourselves know that you are God’s temple and that the Spirit of God lives in you?

-1 Corinthians 3:16

Believers are the dwelling place of God on earth:

In him the whole building, being put together, grows into a holy temple in the Lord. In him you are also being built together for God’s dwelling in the Spirit.

-Ephesians 2:21-22

Before Jesus died, rose, and ascended the Father's house was the physical temple in Jerusalem:

And He said to those who sold doves, “Take these things away! Do not make My Father’s house a house of merchandise!”

-John 2:16

But today the Father's house is the spiritual temple of Christ's body on earth:

Jesus answered and said to them, “Destroy this temple, and in three days I will raise it up.”

-John 2:19

Through the resurrection of Christ, the Father's house, Christ's body now has room and are the rooms of the Father's house.

Jesus and the Father indwell one another.  Jesus went to the cross, died and was buried, rose and ascended, making the temple of God, the Father's house, all believers.

Jesus bridges the gap between his followers and the Father:

Jesus told him, “I am the way, the truth, and the life. No one comes to the Father except through me.

-John 14:6

Jesus' disciples each become the home of God:

Jesus answered, “If anyone loves me, he will keep my word. My Father will love him, and we will come to him and make our home with him.

-John 14:23

And all of Jesus' followers have become God's house, made by Christ through his death:

In my Father’s house are many rooms. If it were not so, would I have told you that I am going to prepare a place for you?

-John 14:2

Jesus went away from being with his disciples so that he could come back and be in them:

If I go away and prepare a place for you, I will come again and take you to myself, so that where I am you may be also. 

-John 14:3

After His resurrection, Jesus brought us into Himself:

In a little while the world will no longer see me, but you will see me. Because I live, you will live too.  On that day you will know that I am in my Father, you are in me, and I am in you.

-John 14:19-20

Jesus is in the Father and now we through Jesus are in the Father.  We are now where He is, in the Father's house.  The rooms are the living being of the body of Christ.  We are now living together with Christ in his home.  We abide with Christ making our home with Him.  The more we make our home with Him, the more He makes His home in us.  The vine in John 15 is the home in John 14:

“I am the true vine, and my Father is the gardener. Every branch in me that does not produce fruit he removes, and he prunes every branch that produces fruit so that it will produce more fruit. You are already clean because of the word I have spoken to you. Remain in me, and I in you. Just as a branch is unable to produce fruit by itself unless it remains on the vine, neither can you unless you remain in me. I am the vine; you are the branches. The one who remains in me and I in him produces much fruit, because you can do nothing without me.

-John 15:1-5

Believers are a building, the temple of God (Ephesians 2:21-22) and we are the New Jerusalem (Revelation 21 and 22).  The goal of our lives in Christ is not to go to heaven but to be the dwelling place of God where we dwell with Him and He with us.  We are the New Jerusalem, the dwelling place of God, which began for believers when Christ went to the cross, died, and rose again.  And that is what John 14 is about.