I think building it ahead of time and getting it just right is a good plan. That way you aren't panicking when he needs to move up and putting him into a substandard enclosure just because you need it in a hurry. I'd think now would be a good time to join a local herp society or something, too, so that if you eventually have no roommate to help, you can maybe find another one through herp contacts who can help you out.