John 14:2 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.

If we look at the following scriptures and examine them carefully, we find that they teach in regards to a building, house, and habitation, all of which are comprised of a group, rather than any single individual.

1 Corinthians 3:9 For we are labourers together with God: ye are God's husbandry, ye are God's building.

Ephesians 2:21 In whom all the building fitly framed together groweth unto an holy temple in the Lord:

1 Peter 2:5 Ye also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ.

Ephesians 2:22 In whom ye also are builded together for an habitation of God through the Spirit.
In this passage, Jesus is likewise speaking in regards to the same building, house, and habitation.

Jesus goes a step further, by identifing the individuals that make up the building, as "many mansions" that exist within the "Father's house".

The word "mansions" is synonomus to the "chambers" of the temple shown to Ezekiel (Ezekiel 40-48). The vision Ezekiel was shown was of the coming Kingdom of God/Heaven, which was to be ushered in by Christ Jesus, and as prophesized by Daniel.

Daniel 2:44 And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever.

This Kingdom of God/Heaven is synonymous with the Comforter. This passage is in the context of the teachings of Jesus to the apostles, concerning the Comforter, which was to come at Pentecost.

In John 16:7, when Jesus stated, "It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you", He was referring to the place which He went to prepare.

Niether the Kingdom of God/Heaven or the Comforter could come, until Jesus had been glorified.

Properly understood, Jesus is speaking in regards to the kingdom of heaven and the multitude of individual believers (Matthew 9:37). Each of these individual, as chambers within the house, would be dwelling places for the Holy Spirit, by which the Father and Son would dwell within each (John 14:16, 17,18, 20, 23, 26, 28, John 15:26).

Related passages:
1 Kings 6:5
Ezekiel 40-48