BTW, 10% of these data collecting advertisements on the real estate websites are from identity thieves.
There's no easy solution. Everyone puts the blame on the landlord saying they should be careful who they rent to, but that's difficult to do without doing some kind of background check on tenants and can also lead to discrimination.
Because that's illegal, even without the rent cap in Berlin.
https://www.gesetze-im-internet.de/bgb/__556d.html
It's illegal here to demand a rent more than 10% higher than the "ortsübliche Vergleichsmiete", which is approximately the local rent averaged over the last 6 years (exactly defined in §558)
More generally, you cannot simply ask for astronomical prices for anything in Germany just because you know that people are in a position where they have to pay them, that's "Wucher" (racketeering) and against public decency, which is generally illegal according to §138.
Another one is vague and based on the "Mietspiegel", which lists appropriate rents according to quality and location.
If the rent exceeds this by too much, you can sue for "Mietwucher" (rent usury).
Berlin had the nice example of a few square kilometers of the Tempelhof airport field being available. Public demanded to make it a park instead of constructing housing.
Almost anything with a tree on it is impossible to build on, and even if there is a building permit for the housing, attaching it to public transports like the S-Bahn or Subway is next to impossible nowadays.
Building codes in Berlin are not much weirder than in the rest of Germany, but they also serve to make constructing housing harder. E.g. there is a strict limit to building height, which limits buildings to 5 storeys (iirc) even in high-demand high-density areas.
Money is especially tight for the state of Berlin, while they get subsidized with lots of money from the other states (Länderfinanzausgleich), they still cannot afford to construct much of the necessary housing or the associated infrastructure themselves. Private investment usually will go elsewhere because the political environment in Berlin is poor. If there is rent control in Berlin and no rent control in Hamburg, of course money will go to Hamburg first.
There is also no political will to fix the above.
What I think is a bigger problem is the countless vacant lots all over the city. Even centrally there are tons of them, e.g. with only a one story supermarket or parking lots (as mentioned above) or sometimes it’s just overgrown. I wonder what the deal are with those. My guess is that the city already sold them in more dire times and now owners just sit on them until the real estate prices makes the time ripe to build something there. Can’t find another explanation for it.
That's exactly what they are doing at a few places in my city (also with a massive housing problem).
We recently found a new apartment here, the process was as follows:
(1) We found the apartment online. It was online for exactly 6 hours, listed by an estate agent.
(2) Inside the listing (hidden deep in the description) was a short sentence saying that any contact made through the listing website contact form would be ignored and that a secret mail address had to be used. You had to email an application letter (preferably with photos), copies of your latest 3 salary statements, copies of your identity card, proof of your credit-worthiness ("Schufa-Auskunft" in Germany), proof that you had liability insurance, and contact information of previous landlords. This had to be mailed until a deadline the next morning. If any of this was missing, the application would be ignored.
(3) A week later, we received an email telling us that we were eligible for an appointment to visit the apartment. But we had to confirm this until the same evening by sending an SMS to a secret number.
(4) A few days later, we indeed got a date and time for visiting the apartment (via SMS). It was a 15-minute slot, but there were at least 10 other families there, and they did visits the entire day. When the agent asked us, we indicated strong interest, told him we could rent the place beginning tomorrow and left.
(5) A week later, we got the apartment (of course we now have to pay 2 rents for 3 months). When we asked him why the process was so complicated, he told us that they were only 4 people in the agency, and they didn't have the capacity to read (not answer!) > 1000 mails of people interested in the apartment. So they gradually came up with various hoops and obstacles to get this number down to something manageable (they got it down to around 50 families who indicated final interest).