Before the financial crisis, housing became an asset class through securitisation. As films such as The Big Short showed, bankers bundled together the income streams from individual mortgages into bonds, which were then sliced, diced and sold off. This worked well until the mortgage industry ran out of good borrowers and went subprime. The resulting mortgage crisis showed investors that securitising mortgages was easy but risky. What was safer, but a harder thing to do, was to acquire the underlying assets – the houses – and rent them out. This involves visiting individual properties, evaluating them, buying them, renovating them and finally renting them.