Even if you put all of your efforts into #2, it will take years from the decision to ramp up the planning and construction efforts until enough houses are actua

Even if you put all of your efforts into #2, it will take years from the decision to ramp up the planning and construction efforts until enough houses are actually built to have a noticeable impact on the market. And you still have to do something about the situation in the meantime. That's why the rent freeze in Berlin is limited to 5 years.