> You can cancel a lease with a renter because of "Eigenbedarf"
Which has a 10 year "Sperrfrist" (freeze period) and you need to go to court if the renter refuses to honor and make your claim. Even in that case you need to prove your personal need and "living in your own property" does not satisfy that requirement.
On the flip side, this means that there is absolutely no need to buy the flat you are living in, because your landlord can't easily throw you out anyway. If you are after the savings in rent, you can still buy a flat and rent it out to pay your own rent.
Which has a 10 year "Sperrfrist" (freeze period) and you need to go to court if the renter refuses to honor and make your claim. Even in that case you need to prove your personal need and "living in your own property" does not satisfy that requirement.