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.
Webinars are quite possibly one of the most potent ways you can make an exorbitant amount of money online. You'll need an audience to train and you'll need to know what you're talking about. Of course, this usually requires having a website and some semblance of an online presence. However, people can still do webinars without all of that. For example, you might have a sizable social media following and you train them every week on something to do with social media. But you will need a product to embed and sell at some point. Don't worry about it in the beginning. In my experience, the best webinar platform out there is GoToWebinar.
Upwork: This website offers a great marketplace for selling just about any professional service. You don't need a merchant account, a website of your own or anything else for that matter. All you need to do is be able to provide a high-quality service at a reasonable price. But be informed, you will have to compete with many others that are constantly bidding on open jobs.
The peer-to-peer concept is coming to virtually every corner of human existence. That includes the hospitality industry. Through AirBnB you can actually rent out your house for various lengths of time for a predetermined fee. That gives you an extra income on your house and gives the visitor the benefit of having an entire house, rather than being crammed into a single hotel room.
Mechanical Turk is Amazon's take on micro-jobs. These are small miniscule-jobs that you can do for other people, which they call HITs, or Human Intelligence Tasks. These are super simple tasks that anyone can do. Some examples are listing off some URLs with certain kinds of images for one cent, or recording a few phrases with a microphone for 6 cents.