Is money earned from building homes financed by an interest-based loan considered permissible (halal) or forbidden (haram)? And does the ruling differ if the interest rate on the loan increased after it was obtained, given that the borrowers knew it was usury when they took it?

Usurious borrowing is unlawful (haram) because it involves a benefit for the lender. Any loan that brings a benefit to the lender is unanimously (ijma'an) considered unlawful. The reason for its prohibition is the increase (riba); if this increase were abolished, it would be permissible. It is not permissible to engage in it before its abolition, except out of a necessity that threatens destruction or extreme hardship. It is permissible to deal with someone who has taken a usurious loan, for the principal of the loan is permissible, and the unlawfulness relates to the increase. The sin is upon both the one who takes it and the one who pays it, and there is no blame on the one who deals with the borrower.