The amount you owe on your mortgage is made up of the original loan, plus the interest your lender charges you for borrowing the money. Your repayment type can be ‘interest only’, meaning you’re paying off the interest each month but none of the original loan, or ‘capital and interest’. Capital and interest means you’re not just paying off the interest, you’re actually making a dent in the loan amount too.
In the case of an interest only mortgage you would need to make other arrangements to ensure you will be able to pay back the capital at the end of the term. If you choose affordable housing you will not have a choice of repayment types. You will have to opt for a capital and interest repayment mortgage.