Try and make it as big as your parents will allow. When it comes to darkrooms bigger is always better. Mine is 18'x12', 4x5 and 8x10 enlargers, 34"x8' sink, plus 12' of countertop. Wish I had another 50sq/ft. My first darkroom did not have a sink, just countertop for trays, basement had a utility sink I used for film and print washing. Size was about 8'x8' and did 11x14's wih 4x5 enlarger. I have also used walk-in closets when in an apartment, but ventilation was a big issue and very cramped and roommates didn't appreciate the smells.