What is the ruling of Islamic law on borrowing money with interest to contribute to purchasing a house with one's sister and her husband, or to buy an apartment and rent it out in a non-Muslim country?

Borrowing with interest is one of the major sins and one of the seven destructive sins. It is not permissible to undertake it except in cases of extreme necessity, such as fear of perishing. Purchasing a dwelling is not considered a necessity. Whoever fears Allah and trusts in Him, He will provide him with good and lawful provision and suffice him in what concerns him.