Purchasing a home in Sydney without a buyer's agent can lead to costly mistakes. Common pitfalls include overpaying due to limited market knowledge, missing out on off-market deals, underestimating additional costs like stamp duty and inspections, ineffective negotiation, and inadequate due diligence. A buyer's agent provides expert guidance, access to exclusive listings, and ensures thorough evaluations, helping buyers make informed decisions and secure better deals in Sydney's competitive real estate market.