You wouldn’t actually look up Mülheim for an accommodation when you’re at a venue in Oberhausen. On the other hand, the venue in Oberhausen is just two minutes away from Oberhausen train station. The b&b Hotel Mülheim is fairly new, clean, and low price. And it’s less than a five minutes walk from Mülheim train station.
The train between Oberhausen and Mülheim is just eight minutes and there are trains going almost all night long.