Is it permissible to lend someone a sum of money to save his house from confiscation, then he leases his house to me at a low price, with the loan contract separated in writing from the lease contract, knowing that the rental price will be lower than the market price due to my financial circumstances?

It is forbidden to combine a loan (Qardh) and a lease (Ijarah (definition)), whether in a single contract or two separate contracts, based on the Prophet Muhammad's (peace be upon him) saying: "It is not permissible to have a loan and a sale." This is because a lease is a sale of usufructs. The wisdom behind this prohibition is to block the means to usury (Riba), because a loan that brings a benefit is usury. If a person leases a house for a value much lower than its real price because of a loan, this is considered clear usury. What is obligatory is to repent to Allah, annul the lease, and reclaim the loan, or increase the rent to its real value to eliminate the usurious interest, and then seek to reclaim the loan.