If you're interested in online marketing, setup email software and create a lead magnet that you can use in your sales funnel. Then, build up that list. It's often said that you can expect to earn about $1 per subscriber per month. If you have a list of 10,000 subscribers, that means you can earn roughly around $10,000 per month. You will need to deliver value and not pitch them on every email, but it is a very achievable goal in a short period.
Please note that some of the links below are affiliate links and at no additional cost to you, I will earn a commission. Know that I only recommend products, tools and learning resources I've personally used and believe are genuinely helpful, not because of the small commissions I make if you decide to purchase them. Most of all, I would never advocate for buying something that you can't afford or that you're not yet ready to implement.
Has anyone ever told you you have a voice for radio? Are you great at creating original characters with just your voice? There are tons of people looking to pay for quality voice overs for their corporate videos, animation series, or educational videos. Check out Fiverr and UpWork or create a profile on a specialized site like Voices.com or The Voice Realm to get started making money online doing voice overs.