Burkard Stevens

i have an apartment the last ten years in Teltow , which the tenant left one and half year ago , and i left her empty hoping my son who became a doctor in Poland will live and work in Berlin , he decided not and now i am putting the apartment for sell. somebody told me now that i might have problems with the authorities in Teltow for having the apartment empty long time. how bad is my situation and what can i do about it.??