I'm in the same boat. The wife begged for this iguana while buying some food for our other animals at Petco last week. I told her it wasn't a good idea. But the damn thing kept following her no matter which side of the enclosure she was on. She was convinced that it was meant to be.
So long story short, we have an iguana now. She didn't realize the size of the enclosure it's going to need when it outgrows the 30 gallon terrarium.
Women, they never listen.
I had 7 or 8 iguanas when I was younger. Most were medium-ish sized when I bought them and they didn't grow much. I think it's because the pet stores don't feed them right? Anyway for whatever reason their growth seemed stunted and slow.
The one iguana I bought when he was super tiny, he grew and grew and grew, super fast. I had a 4 foot long tank and he outgrew it in 2 years. But he also had the best temperament, the longest tail, and all of his spines on his back because I hand-raised him and handled him all the time.