They can't is the straight up answer, unless they are very good jobs. The couple that bought the house next door to us are in their late twenties but one is an officer in the air force and his fiancee is a partner in a law firm so they can afford it. If you are a first time buyer in an average paid job you are buying much further out of London or major cities, but that's life, you can't just buy into a central London house as a first property. Also depends what you call a decent area, you mean in terms of crime stats, country views, transport connections, local high street shops etc.