The first thing you should know is that eventually,m it will be 4-6 feet long and require a very large, very expensive enclosure. You should also know that while some are sweet as pie to people, and will accept being handled, others are not. Some will bite, scratch, and otherwise be rather unpleasant to handle. However, most are okay with being touched, even if they are not thrilled about it.
I had one once that was a nasty thing. But I also had one once that was as friendly as a puppy.

You can't really tell. The nasty one I had came from a reptile specialist pet store, the friendly one was abandoned in my car. She was a wonderful pet. However, I only kept her for a few months since I was not prepared for her at the time, and eventually she went to a permanent home.
They require a lot of equiptment like heating rocks, lamps, special lighting etc. Their food can get costly depending on what you buy, and how much fresh food you mix in. You'll want to start with at least a 55 gallon tank, because in the long run, it will be cheaper than constantly upgrading smaller tanks. Eventually, you may have to go bigger than that. You're probably looking at a few hundred to start off with.
They are fascinating to watch however. And generally, they are at least okay with being handled.
Good luck with whatever you decide. There are many other types of reptiles out there easier to keep though, you may want to check your local reptile dealer. Anoles are small lizards that are a good starter lizard.