Build a property tax-refund calculator for a law/realty firm website

We run a small legal consultancy that advises clients on property purchases, and we want an interactive calculator added to our website so visitors can estimate the tax refund they are entitled to after buying a home. A visitor enters the purchase price of the property and the interest already paid on a mortgage loan, and the tool automatically computes the refund based on the deduction limits that normally apply. The logic must reflect two separate caps that often apply together — one tied to the property price, and a higher one for mortgage interest paid — and combine both correctly.

The result should show a breakdown rather than a single number: how much of the price qualifies, how much of the interest qualifies, and the total refund, in a simple, mobile-friendly layout matching our site. A client-side script or a small server-side piece both work, whichever makes future changes to the limits easier. Accuracy and clearly commented logic matter more than visual flair, since visitors use these figures with an accountant.

What we expect:
— input fields for property price and paid interest, with validation against unrealistic values
— automatic calculation with a visible breakdown of each component
— clean design that fits our site and works on phones
— a short note explaining what is being calculated