As a 15 year old, you can make a lot of money online and fast if you're fluent in English or any native language (Use Cambly), can record and edit great content (YouTube), transcribe audio and video files (Rev and GoTranscript). If you're looking for a long-term source of revenue, you should consider starting a YouTube Channel as you'll only keep getting better at recording, editing and optimization and your videos can keep making you money even after 3-4 years.