Essentially correct if you want to avoid paying mortgage insurance. The figures you've described suggest an 80% loan.
You can borrow up to 90% of the purchase price fairly easily, and in certain circumstances you can borrow as much as 95%. In these scenarios you'll have to pay some mortgage insurance, this can often be added to the loan, but it's not always ideal.
Assuming there's no grants or stamp duty discounts available, and that stamp duty and purchase costs are about 5% of the purchase price, the absolute minimum you'd need is roughly 12% of the property value. The scenario described above comes to about 25% of the purchase price.
The exact figures depend a lot on the specifics of the scenario, such as:
* Is it an investment or owner occupied property
* Are you a first home buyer
* Do you have equity in other properties