It's not all that weird to be thinking about it now, some people do when they're young, but deciding to be a prostitute isn't like deciding to be a vet or a builder. You don't plan your life around it or pick your GCSEs to lead into it. We'd never tell anyone that we think they should be a prostitute, it's a decision that you make yourself, but in your case it doesn't even make sense at this stage for you to be thinking about whether it will be right for you when you're old enough.
If you only want to do it to make money for things you actually want, well that might work, but it's a minority of people who are able to have sex for money and stay happy in themselves. Even if you have the idea now that you'll be ok with that, you're going to change a lot in the next few years *and* the reality of sex work isn't something you can fully get your head around before you try it, even if you have a good imagination. Assume that prostitution won't be a good idea for you and think of other ways that you can make and save the money you need to follow your dreams.