Rescues are always great, but if you rescue one you'd likely end up with a lot of problems(either unhealthy or with some bad habits!), and I don't really recommend buying from petstores. Most babies I've seen on kingsnake are like 15 dollars to 25 dollars. In petstores I've seen them for 5. It's the cost of setup that is where the money goes
I've never seen iguanas at a reptile convention, but a lot of them down here don't allow people to sell green iguanas at a convention(which honestly I'm okay with!)
Sorry if I sounded harsh. It's just crazy how overwhelmed people can get by these awesome animals. I have no doubt you would do more research first, but so did Nathan's family, and no research prepared them for the terrors of their first breeding season! They thought their iggy was psychotic! There is a reason why they are for sale on craigslist all the time when they do survive long enough to get big!
Don't get me wrong, I love our iguana, but oh boy how our lives would be easier if she was something else, lol!