All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Our advice to the questioner, after reminding him to be conscious of Allaah, is for him to be moderate in building his home, and to avoid extravagance and boastfulness.
The Prophet saw a dome on one of the houses of Ansaar (residents of Al-Madeenah who sheltered the Muslims who migrated from Makkah) and said: “Every building will become a liability on its owner except that which is necessary.” [Abu Daawood, At-Tabaraani and Abu Ya’laa]
In addition, ‘Abdullaah bin ‘Amr narrated: “The Prophet passed by us while we were repairing our shack. He said: “What is this?” We said: “The structure of the shack has weakened, and therefore, we are repairing it.” Thereupon, the Prophet said: “I surely believe that the matter is faster than that [i.e. death is faster approaching to you than the destruction of the shack].” [Ahmad, Abu Daawood, Ibn Maajah and Ibn Hibbaan] This narration implies that reforming one’s own deeds takes preference over repairing his weakened shack as death is closer to him than ruin is to his shack.
Furthermore, Qays bin Haazim passed by Khabbaab bin Al-Arat while he was building a wall for himself and said: “Indeed, the believer will be rewarded for every thing that he spent except something that he spent for this dirt [i.e. the dirt used for construction].” [Al-Bukhari]
Accordingly, be keen, dear questioner, to follow moderation while building your home. Build your home to meet your need and save the surplus of your money to build the life to come.
Regarding supplication, we are unaware of any specific supplication from the sunnah for entering a new home. However, the Prophet said: “Whoever dwells in a new place and supplicates, ‘I take refuge in Allaah’s perfect words from the evil He has created’, nothing will harm him until he departs from that place.” [Muslim and At-Tirmithi]
Moreover, be sure to recite chapter Al-Baqarah in your home due to the saying of the Prophet : “Indeed, devils flee away from a home in which chapter Al-Baqarah is recited.”[Muslim]
Finally, we would like to draw your attention to a matter concerning which many people are heedless, namely, building the rest room where the user would not be forced to face the direction of the Qiblah or its opposite. The Prophet said: "When you meet your human need do not face the Qiblah and do not turn you backs to it.” [Al-Bukhari and Muslim] However, some scholars this prohibition is only applicable to meeting one’s human need in the open space, not within a building. Nonetheless, other scholars believe in the general prohibition due to the general wording of the text. Therefore, by following the latter position we stay in the safe side.