Of course you should be prepared. But most people, even after research, don't understand what actually OWNING a Green Iguana is like.
Like I mentioned before, of course its more than worth it to most people, and although I won't ever have another Green Iguana, I most certainly treat Roxy (my current iguana, 5 feet, 6 years) like a reptile Queen.
But the practical side is that if you cannot handle a very rough 5 foot lizard who literally needs a stable sized cage, craps WAY more and messier than a snake of decent size, and eats like a growing child then you shouldn't have a Green Iguana. Roxy eats normally 21-30 full plate sized portions of food per week. That's two-three plates per day of a variety of greens and veggies. That's a lot for some people, including me. I do it of course though!
Anyways good luck making your choice< you may be the type of person who will enjoy your green igiuana and realize that they are indeed worth the trouble. But its always nice to know beforehand what you are getting into