Green Iguana Society Message Board: Self Sustaining habitat

Hi Everyone. I am not currently an iguana owner but I have a close friend who is moving and looking for someone to care for their iguana. She is a female, around 5 feet long, and six or seven years old. What I am interested in doing is creating a self sustaining ecosystem with in a green house to keep the iguana in. I am wondering if anyone has any experience with growing food for an iguana and allowing it to graze as it would in the wild. I have a good idea of the variety of foods I would plant but I am wondering how much plant matter I would need and how much space.

Of course if I take this project on I would still be checking in on the iguana everyday and monitoring its diet.