Ideally, you should save as much as you can before buying a home. The more you save for a home loan deposit, the smaller your loan and the higher your chances of getting approved for a home loan. The amount you need for a deposit also depends on your lender and the loans Loan to Value ratio (LVR). (LVR is the percentage of the loan that you are able to borrow.)
Ideally, you want to have a 20% deposit plus purchasing costs. However, 8% is the minimum deposit with most lenders as this gives you a 92% loan with Lenders Mortgage Insurance (LMI) which will take you to a loan of 95%. There are a few banks that will allow you to borrow with as little as a 2-5% deposit and they typically have higher interest rates.