I have had temporary darkrooms (bathrooms) with running water, and now I have a permanent room without. While fully plumbed hot and cold with drainage would be nice, the permanent space is more valuable. My sink drain drops into a large bucket. For water I bring in a large container with a tap. As long as the volume I bring in does not exceed the capacity of the sump bucket, I'll have dry feet 8-) I do major washing of film and prints in the laundry area of the house where there is a sink and print washer. The print drying racks are in the darkroom.
Putting in water and a drain would be difficult for my setup. If I did a lot of work the need would offset the issues. It is a balance that will be different for everyone.