I purchased a house in Ireland in 1998 by taking a loan from a bank. I know it is a great sin to deal in Riba. My intention initially was to profit from the re-sale of the property. I have come to realise this great sin and evil and truly feel very bad about it.
Currently I am using this house as a family residence and cannot sell it. Rents locally are twice the mortgage but I can afford it. I am trying my best to pay off the loan by using all my savings and hope to complete this task very soon.
My question is if I keep the house after it is fully paid for can I rent it and utilize the money if I move to another country? If I sell it, can I utilize the profit which is four times the purchase price. Is there any expiation for this kind of sin? I will be grateful for the reply.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Taking loans with usury is forbidden.  The one who gets involved in that sin should ask forgiveness of Allah and make sincere repentance towards Allah.  And if one can return the initial amount without adding interest to it, he has to do so; otherwise, he should pay interest as soon as possible, to be free himself from such Haram dealings.

If one repents from his sin of purchasing a house through usury then he may sell his house with a higher price, and may use its rent if he rents it out.

As for expiation for the above sin it is making sincere repentance, asking forgiveness of Allah, and increasing good deeds.  Allah Says (interpretation of meaning): {….Verily, the good deeds remove the evil deeds (i.e. small sins)….}[11:114].

Allah knows best.