Whether for high school students or adults, you can monetize your expertise by teaching people with less experience or knowledge than you in that subject area. You can work with an established group like Kaplan for, say, SAT tutoring, or you could try hanging out your own shingle and making your services known either to students, parents and schools in your community. If you are targeting adults, you can create your own website or list your services with adult tutoring companies.
Become a virtual assistant. Virtual assistants perform a wide range of services for their clients, all of which can be completed online. Depending on the day, they may open and reply to emails, schedule online work or blog posts, write mock-up letters and proposals, or perform data entry. You can look for virtual assistant jobs on sites like UpWork.com and Problogger.net.
If you’re strapped for cash but want to work on your own schedule, you might want to consider becoming a driver for Uber or Lyft. You can drive as much (or as little) as you want and set your own schedule. Plus, you get the added bonus of having interesting conversations along the way (or, at the very least, some fun stories to tell of your travels with strangers).