Buying an apartment off the plan can be very appealing. You get a brand new apartment, often in a building with amenities like a pool and gym and, maybe best of all, you have time to save for it because you won't have to hand over the full purchase price until construction is complete.

As Australia's housing market made its way higher and higher, buying off the plan was an attractive choice for many people because it gave them a property, but also the window to save more money for the down payment.

But with national dwelling prices now down 2.7 per cent in the past 12 months, the environment has completely changed.

Buyers who locked in a purchase a year or two ago, when the market was booming, are now struggling to secure the sale.

"We've seen a couple of instances with our clients where the valuations have come in lower than when the properties are registered," conveyancer Alex Sapounas said.

"They're struggling to seek finance and get the valuations according to what they purchased the property for."

Many analysts are concerned about potential apartment oversupply in parts of Sydney, Melbourne and Brisbane. ( ABC: John Gunn )

Some buyers are finding themselves in a dire situation because they need to find tens of thousands of dollars more than they expected, to complete their purchase.

Bank valuations below purchase price

It is a scenario mortgage broker Luke Camilleri is starting to see regularly.

"The most recent one that comes to mind is probably about six weeks ago in western Sydney," he said.

"They bought about three or four years ago and the valuation came in quite low."

The young couple initially agreed to buy their two-bedroom apartment for $680,000.

But when the bank came to value the property upon completion, it did not value it that highly and so would not lend them as much as they needed.

They had to find an extra $54,000, on top of their deposit and stamp duty.

Mr Camilleri said, in the end, the buyers "had to get creative" to find the extra cash.

He said having these tough conversations with buyers is not easy.

"To someone who it's their biggest investment, or their biggest life purchase, to have someone on the other end of the phone saying, 'There's a problem, it doesn't stack up in the evaluation', you can imagine what runs through their minds and it's quite stressful," he said.

Mr Sapounas said it was not just the value of property making it harder for buyers.

"It's also the lending standards that have changed," he said.

"Two or three years ago, when they went and saw their mortgage broker or banker based on their current scenario, [they were told], 'This is how much we're going to lend you'.

"Now, their actual scenario hasn't changed, but the bank's lending criteria has changed."

It means some buyers are being hit twice — with a lower property valuation and a smaller borrowing capacity.

Risky business

Buyers advocate and bestselling author Miriam Sandkuhler said buying a property off the plan has always been a risky move.

Firstly, there is a risk with the developer.

"The level and experience of the developer is quite significant to determining whether or not the property is going to end up being good quality," she explained.

There is also finance risk.

"The builder and the developer may not actually qualify for the finance or be able to finish the development in a timely manner and those delays can sometimes cause purchasers some issues," she said.

Thirdly, there is market risk.

"If there's a downturn in the market, or if there's an oversupply of stock in the market when the property is finally built, that can substantially affect the value of that property and frequently those values come in under the purchase price of the contract," she said.

In a falling property market, the risks are heightened.

"Think of it like buying a brand new car and driving out of the lot and automatically it's depreciated by 20 per cent," Ms Sandkuhler explained.

"Off-the-plan and new-built properties are a little bit similar.

"You can more or less be guaranteed that approximately 50 per cent of the time the properties may come in under the contract price and therefore somebody's going to settle on it being worth less than what they paid."

You can get lucky

Investor Stephen Kendon bought a two-bedroom apartment in Sydney's inner-west two years ago.

The father of four owns his home and another investment property in Sydney.

In May this year, his existing lender pre-approved his finance for the $725,000 unit.

But two months later, his formal application was rejected.

"We had some abnormal expenses and they were looking at that as if they were standard expenses, but they weren't," he said.

"They were treating our expenses almost double to what they were."

Stephen Kendon had to find a different lender to finance his off-the-plan property purchase after his original lender backed out. ( ABC News )

It struck him as unusual, considering his history with his lender.

"We've got a good history of repaying our loans, we can demonstrate that we can pay the minimum or above on our loans. So, it just didn't make sense," he said.

In the end, he was able to secure a loan with another provider, but his experience shows the banks are increasing their scrutiny.

Mr Sapounas expects stricter conditions to remain for the next couple of years.

"I think we've got another year or two at least before we see the market find its footing," he predicted.

"At the moment it's like catching a falling knife.

"No-one wants to be out there catching a falling knife."