Form validation - Mortgage repayment calculator using React

I went a bit beyond the original requirements by implementing typo handling. Although it was a small addition, it taught me a lot about managing state. For example, I asked myself: How should I display error messages for each individual field? What if each field has a different type of invalid input—one is empty, while another has a typo? This made me consider how to structure and manage state in a more flexible and scalable way.

I've already done some basic refactoring, but if you spot any areas where the code could be further improved—especially to reduce repetition or make it more reusable—I'd really appreciate your suggestions!