My darkroom is in a semi-permanently converted bathroom, in that it's not functional as a bathroom, but, so far, no permanent changes have been made to the room or fixtures. It measures about 6 x 8 feet. I installed a pre-fab countertop along the outside wall that extends into the tub, and a second one right angles that is in the tub. These support the enlarger, paper storage and a Nova processor, with a bit of space open for trays if I need. Also, I've added shelving in every bit of available space otherwise. Over the top of the tub enclosure is a purpose-built drying screen
The vanity/sink has print wash trays, or I can set up a Jobo at the sink.
I do 35, MF, 4x5 formats and prints up to 11x14

One of the problems I'm running into is that the chemicals are corroding the drain hardware, in both the sink and the tub. The metal parts are consumer grade stainless trim over plastic, but the stainless isn't up to the task.

I'll post some pix later on.