In Australia, as in most places, waterfront property comes at a premium. But to see the full effects of high-cost Australian housing, look beyond trophy homes on Sydney Harbour and beach pads in Bondi. In cities across the country, tents and other makeshift shelters are springing up by the water. They are the dark side of a housing market that has held firm despite rising interest rates. For households of all incomes, the share of homes that are affordable is at its lowest in 30 years.