Home ownership is moving further out of reach with Sydney ranking among the top three most expensive cities in the world.

However a study has found in some Sydney suburbs, it’s cheaper to buy than rent.

Agents in Sydney's west say low interest rates and demand for rental properties that help to make mortgage repayments cheaper than rents.

Repayments in suburbs such as Ambarvale and Fairfield can be around $380 and $415 per month cheaper with mortgage.

Renting is often more expensive in Campbelltown, Parramatta, Blacktown and Penrith.

Estate agent Mark Hurley told 7News "You own the property, you've got security of tenure. No one's going to come and ask you to move at a months’ notice."

However for buyers, new comparisons to markets overseas suggest Sydney housing is very close to top dollar.

Out of seven countries, Australia is the second most expensive behind China to buy a house and Sydney real estate is a big reason why.

Hong Kong is priciest for a home, followed by Vancouver and then Sydney. Melbourne is in 6th which is well ahead of New York and LA.

Dr Andrew Wilson from Australian Property Monitors says: "But buyers still find a way into the Sydney market and that reflects the very strong aspiration for home ownership."

Figures today show house prices lifting to near 15 month highs.

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