How does that change if 100m people want to live in a city that realistically houses 10m? A bit of an unrealistic scenario, but my city has a very low vacancy

How does that change if 100m people want to live in a city that realistically houses 10m? A bit of an unrealistic scenario, but my city has a very low vacancy rate, and you can't live there on minimum wage / just above. There are just too many people making more money.