I never understand those calculations. You can buy houses in Berlin from around 350k. Maybe not in that area you are looking but still. With something like 600 to 800 sqm ground, house around 100 sqm, quiet neighborhood, 10 min walking to S-Bahn (i.e my grandmothers neighbors house that was sold a few month ago). Probably add 100k for renovation. But with 3.5k of savings a month (from 6.5k easily possible), you have paid it of in ~10 years.
Close to S-Bahn but then more than 1h commute?