marciofs,
I actually did this once and it made a very satisfactory darkroom in an apartment in Pasadena, CA... In a room with two beds. I used thin wood maybe 1x2's and built several frame panels just snug to fit floor to ceiling. I tacked thick black plastic sheeting to the panels. I was lucky to have a room with two walls (can you trade rooms with a flat-mate for one with two walls?). I made an "L" shape darkroom in the big corner of the room with walking room by my bed on the short side of the "L" and then a light baffle door by using another panel snug against my bed which was under the window. My room-mate's bed was by the door, against the long side of the "L". I built a ventilation tunnel above the light baffle and used a large box fan to pull air out at the top.
Since it was "press-fit" it didn't really damage the walls and ceiling, but I don't remember if I ever got my deposit back... In the end when I moved, I think I threw it all away except for the fan. The next place I lived was in the mountains and I had a whole room for the darkroom.
It was really cheap, light-tight, and cool.