Lenders describe a deposit as the other side of the loan to value ratio, or LVR. If you borrow $560,000 against a $700,000 property, your LVR is 80% and your deposit is 20%. That single ratio drives almost everything about your application: whether you pay mortgage insurance, which lenders will look at you, and what rate you are offered.
Twenty per cent is the number everyone quotes because it is the point at which Lenders Mortgage Insurance stops applying. It is a threshold rather than a requirement. Loans are routinely written at 90% and 95% LVR, and the guarantee schemes go further again. What changes below 20% is not whether you can buy, it is what the borrowing costs you.
Two details catch first home buyers out. The deposit you need to complete the purchase is not the same as the deposit you hand over at exchange, which is typically 10% of the price and is part of, not additional to, your total. And most lenders want to see genuine savings, meaning funds you accumulated yourself over roughly three months rather than a sudden lump sum, although a documented gift or an inheritance is usually acceptable with the right paperwork.