@Pete: I can't remember any Pension in OB except for a fairly expensive hotel.
Googling "Hotel Pension Oberhausen" leads to some interesting results.
I assume your concert is going to take place in the ARENA Oberhausen, right next door to the Centro shopping mall.
Public transport to there is great, and the "Centro" train stop is architecturally uh interesting. The tram goes straight to the Centro from Oberhausen train station; there is also a direct tram connection to the Mülheim station, and buses to Bottrop and some other places.
... so anything close to the station would be great; and anything within walking distance to Mülheimer Straße would probably be good, since the tram mostly follows that road.
Sterkrade is in the other direction, but also an option.
Now keep in mind I've never been in any of these hotels, but this list could give you some starting hints:
Harlos, Hagedornstrasse, estimate 22 Eur/night. http://www.tourisline.de/travelstore/control/...
On the Google Map, Hagedornstrasse is only a few minutes' walk north-west of the Arena.
Says it's 5 km from Centrohttp://www.pension-erica-oberhausen.de/
EUR 40 a double room, minimum stay 2 nights
I have no idea how reliable the following lists of places are:http://www.staedte-info.net/oberhausen-ob/hot...http://www.pension.de/stadt-pensionen/Oberhau...
(EZ = single room, DZ = double room). Good luck and hope you enjoy your stay.