Foster rat coming wednesday... Brings total to 4

[PA_Ratopia]

Well, its finally happening, my summer foster rat is coming on wednesday I think. His name is chaucer, he is a 2+ yr. old beige hooded who has been living in a college dorm. I just have NO idea where to put the little blighter... I think right now he's in a 10 gal. aquarium, so he definately needs to be re-housed. Should I just go ahead and order my second R-690??? I chopped my other one in half so I could have boy & girl rats, but now I have a girl and two boys who all have to have separate cages (the boys don't get along, even thoug htey're half brothers)... And now poor chaucer's coming! My youngest rat is living out of a plastic rubbermaid bin with a modified chicken wire top. What to do?! I'm seriously hoping Chaucer and Chevy get along, then maybe i can just make a cage? Any sites about good cage making?