Praise be to Allah.Borrowing with interest is considered one of the greatest of the major sins (al-kabaa'ir). The Prophet (Peace Be Upon Him) has cursed those who consume interest, and those who pay it. Borrowing money with interest is considered as peddling in it as the borrower pays it to the borrower. Whoever does this is to repent and express remorse, and he is to try as much as he can to return only the principle he borrowed without the interest, advising the person who lent him the money against this practice. If he cannot, as in the case of borrowing from interest-based banks, which rarely forgive but rather get back their dues even if by force, he is to return the principle plus the interest offering repentance to Allaah at the same time.
Whatever the borrower has bought or developed in terms of legitimate and Islamically-permitted business based on the borrowed money, can remain in his possession. He is allowed to continue his enterprise and profit from it, paying sadaqah at the time on a frequent basis to purify his business and himself of the misdeed he has committed. Those who work in businesses functioning on money borrowed using interest for which they are not responsible can continue to work in such enterprises as long as the nature of the business is halaal and legitimate such as a Laundromat, etc.
Allaah the Most Knowledgeable knows what is most correct and best.