Been there and done that. 

This picture cracked me up of a bathroom/darkroom.  It brought back not so fond memories of trying to use our families only bathroom as a darkroom when I still lived at home with my parents and younger brother.  This set up seems to have an elaborate rack support for development over the bath tub on the right that can be taken down when not in use.  I like the close proximity to a sink on the left and a toilet of course can be handy but not essential.  If this were a second bathroom or you lived by yourself (and want to remain that way) and are very, very neat this might work.  I suspect this is a new set up or is infrequently used because the place looks so clean.  My darkroom after 5 years of regular use is a chemical stained and corroded mess which you hardly notice under safe lights.  Also the drawback to any darkroom that has to be put together before you start working can be a pain since where do you store your gear and chemicals when not in use, and how long does it take to set up before you can begin working?  Serious drawbacks.  This would probably be the only alternative for an apartment dweller sort of like that closet darkroom the weird stalker boyfriend that Elaine had on a Seinfeld episode.