ANZ's boss has floated the idea of giving Aussie homebuyers longer mortgages as a way of getting them into the market without crippling them financially. Shayne Elliott said more options should be on the table in the industry if we want more Aussies to get the keys to their castle.

According to the Herald Sun, the banking chief said there's technically no law stopping lenders from signing people up to 40 or even 50-year mortgages. But Rate City research director Sally Tindall told Yahoo Finance that locking someone into a home loan for more than half of someone's life would be problematic.

"The idea of shackling, particularly young Australians, to a mortgage for that long is quite an extreme option, but also it will translate into hundreds of thousands of dollars extra that you end up paying over the life of your loan to your bank," she said.

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While, extending the mortgage by 10 or even 20 years would result in smaller weekly, fortnightly or monthly repayments, the interest you would be forced to pay would be much larger.

Tindall said Aussies already do this when they refinance their loan, but it should be approached carefully.

"It's a very costly exercise, and one that should be avoided at all costs," she explained to Yahoo Finance.

"There are different ways to get people into the mortgage market. Seeing them pay tens, if not hundreds of thousands of dollars more to their bank is not one of them."

Plan could burn a $114,000-sized hole in your wallet

Rate City revealed that if you have a 40-year $400,000 mortgage with an interest rate of 4 per cent, the difference between that and a 30-year loan is staggering.

While you would only pay $1,672 per month for the longer loan, compared to $1,910 for the 30-year one, you would end up having to pay $114,962 more in interest during the lifetime of the mortgage.

Loan terms of that length could only really benefit younger borrowers, Tindall said.

"Once you pass the age of 35, a lender may start to consider your profession and retirement age when assessing your home loan application more carefully," Rate City said.

"Different lenders may have different policies on the maximum age they’ll accept for customers seeking long home loan terms. Your chance of approval may vary based on your personal and financial situation."