Considering you have to write about a teen who wants to earn money, make it interesting at least.
You can have the teen (male or female) struggling to get money as they are handling high school, sports (if you want to make them do sports), and other things.
Everybody knows that it's definitely a struggle to be a student and work at the same time, but in the end it eventually it pays off. I'd base this idea off of society nowadays, where teens become pregnant to just get free money off of the government because they're a single mom. How about the teens who actually want to do something in life?
- I'd start out with the teen a month into their job they have at the moment, juggling exams in school and other classes. Maybe they eventually figure out that the job they have currently is doing no good for them (insert a low pay check?). They are soon to graduate, and don't know if they can afford a college to go to. They decide to resign from their job and search for another, even if it's short time such as doing things for neighbors (mowing, babysitting, etc). They eventually find a job where they feel appreciated at and happy to work for. Soon enough, after all of the hard work they have been put through and done, they finally have enough money to pay for a college tuition, a college that they actually wanted to go to in the first place. I'd suggest to add in friends along the way that help the teen get motivated and where they are today.
It's just an idea, but this would be definitely something I would write about.
I would write something with a really touchy topic onto why the teenager wants to raise money. Maybe the main characters boyfriend/girlfriend dies of some disease, or maybe the teenagers younger sibling is suffering from some disorder without a cure. I think it would be a sweet topic, and make it more interesting if the teenager was trying to raise money to find a cure or to support a foundation. You could definitely include sensory language, details and dialogue to propel your story with a topic like this. I think this would be an easy topic to be creative with, and develop. Hope this helps! Let me know if you need anymore help, I love English and I am happy to help you write it! :)
