How a Mortgage Works: A Plain-Language Guide

A mortgage is a loan secured against a property. The lender provides the funds to purchase the home, and you repay the loan with interest over an agreed term, typically 20 to 30 years. If you stop making repayments, the lender has the legal right to take possession of the property and sell it to recover the outstanding debt. This security is what allows lenders to offer mortgages at lower rates than unsecured loans.

The Key Components

Principal: The amount you borrow. If you buy a home for $400,000 and pay a $80,000 deposit, your principal is $320,000.

Interest: The cost of borrowing, expressed as an annual percentage. On a 25-year $320,000 mortgage at 6%, you would pay well over $300,000 in total interest over the life of the loan.

Term: The length of the loan. Longer terms mean lower monthly repayments but higher total interest paid.

Repayment: The regular payment you make, usually monthly or fortnightly. This covers both interest and a portion of the principal.

How Amortisation Works

Most mortgages are amortising loans, meaning each repayment covers both interest and principal, and the balance gradually reduces to zero over the term. In the early years of a mortgage, the majority of each repayment goes toward interest because the outstanding balance is high. As the balance falls, more of each repayment goes toward principal.

This structure means that making extra repayments early in the loan term has a disproportionate impact on total interest paid. An extra $100 per month in the first year of a 25-year mortgage can save several times that amount in total interest over the life of the loan.

Interest-Only vs. Principal and Interest

Standard mortgages are principal and interest (P&I): each payment reduces both the interest accrued and the outstanding balance. Some lenders offer interest-only (IO) periods, typically for investors, where you only pay interest for a set number of years and the balance does not reduce. IO loans have lower repayments during the IO period but require higher repayments when the P&I period begins, and you pay more total interest over the life of the loan.

Loan-to-Value Ratio (LVR)

The LVR is the loan amount expressed as a percentage of the property's value. If you borrow $320,000 to buy a $400,000 property, your LVR is 80%. Lenders use LVR to assess risk. A higher LVR means you have less equity in the property, which increases the lender's risk if property values fall. Borrowers with LVRs above 80% typically pay higher rates and may be required to pay for lender's mortgage insurance (LMI).

The Application Process

Getting a mortgage typically involves applying with a lender or broker, providing documentation of your income, assets, debts, and identity, having the property valued by the lender, and receiving a formal offer subject to satisfactory valuation and checks. The lender will also conduct a credit assessment and stress-test your ability to service the loan at a higher rate than the current one.

What Happens If You Miss Repayments

Missing a repayment will typically trigger a late payment fee and, if missed repeatedly, result in the lender issuing a formal notice of default. If the default is not resolved, the lender can commence repossession proceedings. Contact your lender at the first sign of difficulty. Most lenders have hardship provisions and are more willing to work with you early than after the loan is significantly in arrears.

Key Takeaway

A mortgage is a long-term commitment. Understanding how interest accrues, how amortisation works, and what your LVR means will help you make better decisions about loan structure, term length, and repayment strategy. Even modest extra repayments made early in the loan can reduce the total cost and duration significantly.