Let not your heart be troubled: ye believe in God, believe also in me.
 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.
 And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
The traditional view:
1. The Father's house is Heaven.
2. When Jesus ascended back to Heaven He started a construction project so that every believer will have their own mansion ("I don't know what it will be like, but if Jesus has been working on it for 2,000 years..."). But, He said “ARE many mansions,” not “WILL BE after I go build them.”
3. Christ is teaching His disciples about the rapture of the Church.
One of the major hinderances to Bible study is reading truth back into a passage before it was revealed. The way this passage is usually taught is a great example of anticipating revelation. It is easy to read the Body of Christ and the rapture into this passage, but the Body of Christ and our rapture were mysteries revealed through the apostle Paul (Eph. 3:1-12; 1 Cor. 15:51-52).
• In my Father's house
Christ referred to the temple in Jerusalem as His Father's house (Jn. 2:16). Some teach that in v.2 Christ is referring to the temple that will be in Jerusalem in the Kingdom Age (Ezek. 40-42). But most of those teachers also claim that the word "mansions" should be translated "rooms.” The King James Bible is perfect and not one word of it should ever be altered. Prophesying of Christ, Isaiah predicted, "And they shall hang upon him all the glory of his father's house, the offspring and the issue..." (Isa. 22:24). The Father’s house is the house of Israel.
• are many mansions
One of the definitions of a mansion is "the house of the lord of a manor.” A manor is "the land belonging to a lord or nobleman.” By saying there were many mansions in His Father's house, Christ was saying that there were plenty of opportunities in redeemed Israel to reign with Him in the kingdom of heaven (see the parable in Lk. 19:11-27). There will doubtless be many mansions in the New Jerusalem which will descend out of heaven after the Kingdom Age (the city will be 1,500 miles square). The names of the twelve tribes of Israel are on the gates of that great city (Rev. 21:12).
• If it were not so, I would have told you
Why would the Lord have to make such a statement to His apostles? They had forsaken all to follow Him, so He was reassuring them that it will payoff in the kingdom (Matt. 19:27-30).
• I go to prepare a place for you
Before they could receive this promise, Christ had to prepare a place for them in the kingdom of heaven. He was going back to the Father by way of the cross. Through His blood He would prepare a place for them in the kingdom of heaven (Rev. 1:5-6; 5:9-10). Israel will enter the kingdom under the blood of the New Covenant. Of course, at this point the apostles did not understand the cross (Lk. 18:31-34). The kingdom was “prepared… FROM the foundation of the world” (Matt. 25:34). In regard to the prophetic kingdom program of Israel, Christ is said to be “the Lamb slain FROM the foundation of the world” (Rev. 13:8). In contrast, the mystery of the Body of Christ was planned “before the foundation of the world” (Eph. 1:4).
One of the definitions for the word place is an "office or official position" (Jn. 11:48). When Christ sets up His kingdom there will be no more place for Gentile kings (Dan. 2:31-35, 44). The twelve apostles will reign as kings, and the faithful Hebrew saints will rule with them over the Gentile nations (Rev. 2:26-27).
• And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also
Does this sound like 1 Thess. 4:16-17? Things that are similar are not the SAME. Christ never taught the little flock of believing Israel to look for Him to secretly rapture them up to heaven before the tribulation! He prepared them for the tribulation (Matt. 24), and told them to watch for His return to the earth after the tribulation. When He comes comes again to the earth, He will send His angels to gather Israel together from the four winds (Isa. 43:1-7) so they can reign with Him in the land of promise (Matt. 24:29-31).