Most of my students are online, but only since the last 3 years. If you are considering teaching online you can advertise here for free https://online-teacher-directory.com/ If you want more local students it may be a good idea to get involved with your local community, In my HO this is much better than any advertising. Maybe have a meeting with your local schools, offer a music club, accompany a local choir? I think one hour voluntary work will pay off with the contacts you will make, these contacts will then help you spread the word about your classes. Good luck in finding new students
Maybe start a pyramid scheme, offer a discount to students who get you new clients.
What are the going rates through the online teacher platform?
Well I usually offer a free lesson for it, but interesting. You'd have to be careful you don't just get a bunch of dead-ends and wind up giving huge discounts to your long-term clients, though.