In finance, a loan is the lending of money by one or more individuals, organizations, or other entities to other individuals, organizations etc. The recipient (i.e. the borrower) incurs a debt, and is usually liable to pay interest on that debt until it is repaid, and also to repay the principal amount borrowed.
Yes, it is permissible to buy a house on mortgage from a non Muslim bank.
This is according to the most learned scholars who are known as Maraaji' of Taqleed.
You can pay the Khums of that amount now (on the date of your Khums) if you are sure that it will be returned to you, or wait until it comes back to you then pay its Khums.
1. Repeating Estighfaar day and night, especially during Sojood and when are away from people.
2. Being busy in Du'a and Tasbeeh and Quran between Fajr and sunrise.
3. Seeking from Allah (SWT) near your parents and requesting their Du'a for you. If they are dead then near their graves.
4. Reciting Sura Yaseen every morning and Sura Al-Waqi'ah every night.
5. Seeking the Shafa'ah from Ahlul Bayt (AS).
If you take the money from a Non Muslim bank and use it in lawful way, then it is allowed.
If you take the money from a Muslim bank, then you must have with them an agreement within the frame of Islamic rules of business.
Yes you can continue to pay Khums each year despite having a mortgage and adjust the monthly mortgage amount as expenses.
A woman, single or married, is independent in her takaleef and obligations towards Allah ta'ala, even in financial matters.
A wife is not obliged to financially contribute to household expenditures, however she is able to do so out of her kind generosity and good-will. She is able to count that as her common expenses.
As for long-term loans, and her contributing to getting it paid of, it will not exempt her from khums should she have anything entitled for khums on her khums day.
And Allah knows best.