父はお金が不足して、借金をしなければならなくなった。

、。

My father ran short of money and had to borrow.

Literal

Father [topic-は] money [subject-が] insufficient [and-して], debt [object-を] do-must became.

~なければならなくなった stacks obligation (~なければならない = must) with change of state (~くなる = came to be). The result: 'came to have to borrow.' 借金をする means 'to borrow money / go into debt.'