Give preferential tax treatment to income from investment, remove any regulations on trading on housing real estate or land ownership concentration, and lower interest rates to made passive investment strategies unappealing thus incentivising wealthier people to go into assets such as real estate, so that over time house prices shoot up and lower income people stop being able to move and they and their descendants are stuck doing low income jobs.
Certainly that's how it works in real life, though I'm not sure of Cities Skyline has a deep enough simulation for that.