How Do Mortgages Work? A Simple Guide

July 22, 2026 6 min Finance

You want to buy a house that costs $300,000. You have $60,000 saved. A bank gives you the remaining $240,000. You pay them back slowly over 15 or 30 years, plus interest. That’s a mortgage.

But there’s more to it. Let’s break it down.

The Basic Parts

Every mortgage has four components, often called PITI:

Principal – the actual amount you borrowed ($240,000 in our example)
Interest – what the bank charges you for lending the money (like a rental fee for using their cash)
Taxes – property taxes your local government charges
Insurance – protects the bank (and you) if something happens to the house

How Interest Works

Here’s the part most people find confusing. If you borrow $240,000 at 6% interest over 30 years, you don’t just pay back $240,000 plus 6%. You actually end up paying about $518,000 total. That’s more than double.

Why? Because interest compounds. Each month, the bank calculates interest on whatever you still owe. In the early years, most of your monthly payment goes toward interest. Only a small portion reduces your actual debt.

Fixed vs. Adjustable Rate

Fixed rate means your interest rate stays the same for the entire loan. Your payment in year 1 is the same as year 30. Predictable and safe.

Adjustable rate (ARM) starts with a lower rate that can change later. It might go up or down based on the economy. Lower payments at first, but riskier long-term.

The Down Payment

The money you pay upfront (our $60,000) is the down payment. The bigger your down payment, the less you borrow, and the less interest you pay overall. Most lenders want at least 3-20% down.

If you put down less than 20%, you usually need to pay PMI (Private Mortgage Insurance), which protects the lender in case you stop paying. It’s an extra monthly cost that goes away once you’ve built enough equity.

What Happens If You Can’t Pay?

If you stop making payments, the bank can take your house through a process called foreclosure. This is why banks are careful about who they lend to – they check your income, credit score, and debt before approving you.

The Bottom Line

A mortgage is a tool that lets you buy a home you couldn’t afford to pay for all at once. The trade-off is that you pay significantly more over time due to interest. Understanding the terms before you sign can save you tens of thousands of dollars.