For pt/pd printing, space requirements are very minimal:
UV light source - mine is homemade fixture comprised of several BLB bulbs, and located on shelf under counter. Its connected to a Gralab.
Sensitizing/coating space - mine is just a cast-off thick sheet of glass placed on a counter.
Paper drying - I use the relatively light tight clamshell boxes from office supply, and place them on shelf above counter.
Bottles for chemicals - I have 7 one liter amber bottles for Dichro method and 3 plastic bottles for the clearing agents. Shelf above utility sink.
Space for use of 2 processing trays - one for developer and other for clearing baths.
Rinsing area - I use hose tray in utility sink for smaller prints and a larger hose tray on stand in garden area for larger prints.
As far as light, one of the nice features of alt processes is the minimal level of control of light needed for the processing area. Its not like whats needed for enlarging papers. My space is in garage, and the translucent panes in door are covered with dark-out cloth. A couple of 25W yellow bug bulbs make navigation in the space very easy.