Signing a contract means that your offer is accepted by the vendor. As soon as the contract is signed by the vendor, the contract is said to be exchanged and this is the official date for your property purchase transaction.
Depending on which state do you live in, we have different property conveyancing laws. If you are in NSW, for example, you leave a 0.25% deposit while signing the contract and you will generally have 5 days of cooling off period. During the cooling off period, the following things happen: