Not only is it extremely hard work, but, if you can get an agency to represent you, which is the first big hurdle, for the first few years it's mostly unpaid work unless you go into catalog modeling, which is looked down upon in the high fashion world. You're expected to work for free, fending off creepy photographers and the like, in order to "build up your portfolio" while spending your time and money going to go-sees, eating nothing to keep your weight down, and, if you're "lucky" enough to be successful and get noticed, putting your education on hold and having to travel overseas alone to live in a tiny apartment with other models, doing the same thing over and over again while waiting for your really big break (which never comes for most people).
It may seem glamorous to outsiders but modeling isn't at all what it's cracked up to be.