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.
Are you good with research and data? Are you an expert in any particular facet of business? If so, this could be a windfall for you. Trust me. I do a lot of this myself. I use my experience and expertise as an entrepreneur to offer clients advice on how to launch their own businesses. I do it all virtually, and I usually charge around $200 an hour for the service.