The first thing is to look in places without good transit as germans (reasonably!) prefer those. The moment it requires owning a car anything outside Berlin (so in Brandenburg) will be affordable.

Here's a quick search for houses under €100k with at least 100m^2 and 3 rooms (2BR) in Brandenburg: https://www.immobilienscout24.de/Suche/de/brandenburg/guenst...

It returns 83 results & while not all of them are within 1 hour drive from Berlin, at least a bunch of them are.

Also if you're in the affluent south or west of the country (which I suspect is where you searched?) you will have far fewer options for cheap housing than in the depopulated former East-Germany around Berlin. You definitely can't repeat this "trick" outside of Munich.