There is an A&O hostel very close to Dortmund Hauptbahnhof central station. If you can't move in to your permanent accomodation on the first days after your arrival, we recommend following this procedure:
How to get the 10% discount at A&O Hostels:
1) The discount is only available for "FLEX: PAYMENT ON CHECK IN" bookings. If it doesn't look something like this, the option probably not available any more.
2) During the further booking process you will come across this box, enter "ESN2015" to get your 10 % discount!
Note: This offer is only available if you pay cash!