I was scouted by an agency when I was a teenager and went on to do a few fashion photo shoots and adverts. They were fun and I very much enjoyed telling people I was a model but...
...The pressure to look a certain way was enormous, particularly to keep your weight as low as possible.
...The pay was actually pretty shit. For a whole day shoot I'd be paid about £250 (this was the early 2000s) but would usually have to travel to the shoot at my own expense and hand over a percentage to the agency. The days could also be up to 14 hours of sitting around in freezing cold studios wearing whatever get-up they wanted you to no matter how uncomfortable. You couldn't really negotiate more pay or better conditions because the manager would just tell you to get off-set and replace you with another random tall, slim pretty teenage girl of which there are hundreds.
...There were many many creepy men that needed to be almost constantly fended off. Those offering better opportunities in glamour modelling were the worst.
...It's very hard to build a career in modelling because the work is patchy so you need to have another job or juggle it with college. This is okay but then there's a risk you get a reputation as being inflexible and, again, the agency will stop asking you to do shoots if you say no because of other commitments.
...It is horrible for your self-esteem. Many many people will be constantly telling you you're too fat, your legs are too chunky, your boobs are too small, your eyes and too close together, your hair is too short, your toes are too long. I was on a shoot once and the manager looked me up and down and, in front of everyone, said 'What the fuck is this thing?' 
Would I recommend doing modelling? Yes, I would. I had some great times with other models and know a few who've gone on to have it as their full-time job (though are now struggling now we're all in our early 30s). I'd say go for it but go into it with your eyes wide open and be ready to quit as soon as it gets too much.