Is it permissible to resort to usurious banks that apply the "Islamic Murabaha" formula (ownership then lease ending in ownership), or to own a house and mortgage it to the bank with a fixed murabaha that does not involve compound interest, for the purpose of buying a home in Jordan, due to Islamic banks refusing to finance me for reasons related to my husband's work situation in Sudan, and given my dire need for housing for myself and my children?

The basic principle is that it is not permissible to deal with interest-based (usurious) banks. However, it is permissible to deal with them out of a recognized necessity, such as the absence of Islamic banks, or for a need that Islamic banks do not fulfill. This permissibility is limited to the extent that the necessity is met. There is no objection to dealing with branches of interest-based banks that are entirely independent in their Islamic transactions. If Islamic banks refuse to engage in a transaction that is permissible, then there is no objection to it, while being careful about usurious late payment penalties. We do not advise using Ijara Muntahia Bittamleek (lease-to-own) with non-Islamic banks, due to the high probability that the Sharia conditions are not met therein. The safest approach is for the bank to buy the house first, then sell it to you in installments on a Murabaha basis, with the house mortgaged to the bank.