I've had two iguanas, long ago, and they were both very different from each other. One was a female who I got fairly young, for free, after the pet shop were unable to sell her as she was lost her tail and wasn't "as pretty" as the others. She was the sweetest thing, very very gentle, would go along with everything. She loved crawling under the covers of my bed, or under a blanket, and press up against me for body heat.
The other was a rescued adult male, who hadn't come from the best of homes. He was very aggressive towards everyone but me. He liked his space, liked to do his own thing, but was very pleasant to live with (I lived alone at the time).
The female lived in a large terrarium, I can't remember the size. The male had never lived in an enclosed area, we think, and hated if we closed the door to the terrarium, so he basically roamed free in my flat (except for the kitchen, as he jumped everywhere to explore and it wasn't safe). I built him a corner unit with a shelf and a heat lamp where he spent a lot of his time. He also absolutely loved napping on a pillow on the window sill. He was very very receptive to my body language and voice, so I could stop him from attacking guests by telling him no, or by sitting between him and the guest. He kind of learnt toilet training, or at least learnt that I wanted him to pooh in a plastic cat litter tray. But he never really understood that I wanted him to do it ON the tray, so often he'd sit on the side of it and pooh down onto the floor. Still, better than on the bed! But you can also stimulate them to go if you give them a bath, and as long as you do it at least once a day, that'll probably work.
An angry adult green iguana isn't to be toyed with, their tail is sharp and they wield it as a whip. Their teeth aren't pleasant either, I've been told. But, they're fairly clever, and from my experience, receptive to body language even when it's a human.
