Final answer:
A restrictive loan of a fixed amount that cannot be prepaid or renegotiated without taking out a new mortgage is called a non-amortizing loan or a non-prepayable loan. This type of loan typically has a fixed term and fixed payments throughout the term.
Step-by-step explanation:
A restrictive loan of a fixed amount that cannot be prepaid or renegotiated without taking out a new mortgage is called a non-amortizing loan or a non-prepayable loan. This type of loan typically has a fixed term and fixed payments throughout the term. It is important to note that the term 'restrictive loan' is not commonly used in finance terminology, but the description provided matches the characteristics of a non-amortizing loan.