Sydney agents and owners are weighing up the findings from Reserve Bank economists Peter Tulip and Ryan Fox, who have said that Australian property prices are 30 per cent undervalued.

Dr Tulip revealed the figures on Wednesday, saying the annual cost of renting was likely to be 3.9 per cent of the property's value, compared with 2.7 for owning.

Shannon Whitney, CEO of BresicWhitney real estate group, agrees that "in the current low [mortgage] rate environment, there's a very strong agrument for that".

"And when one compares the cost of living and rents in Sydney, I think there's probably a fair basis to that statement."

Also citing the lack of housing stock in the market and investors continuing to drive demand, Mr Whitney thinks the current conditions are likely to persist.

Balmain couple Garry McDougall and Virginia Nightingale, about to sell their house and rent while considering their options, are not worried.

"Predicting the future is a mug's game," Mr McDougall told Fairfax Media. "We've been here 29 years. There's a time to move on and maybe this is it. It's probably a good time to sell as well."

He is confident in the decision to sell: "I can't predict the future so if surprises keep arising, so be it. You do what you can. No regrets, that's my attitude."

He believes that, while it's better to own in the long run, there is nothing wrong with renting in the short term. They will use that time to consider whether to downsize or even buy two properties. For them, the difference between owning and renting is "not much''.

Their agent Megan Smith, with Belle Property Balmain, is cautious about Dr Tulip and Mr Fox's findings.

"I wouldn't say house prices are 30 per cent undervalued, especially in the inner west. Growth's been fairly steady."

She does agree that people should be choosing to buy if they can.

"I think it's advisable for people to invest in property, but not everybody is in a position to do so. If you are in a position to do so, definitely do."