In 2017, there were almost 90 million pet dogs in the US. Which has opened up a huge opportunity to make money online as a dog watcher or sitter. Specialized sites like Rover or Care.com connect pet owners with pet walkers, sitters, and boarding houses to help look after their best friends when they’re at work or on a trip. If you’re an animal lover, you can make extra money and get to spend some quality time with a furry friend.

Upwork: This website offers a great marketplace for selling just about any professional service. You don't need a merchant account, 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. 
Creating and selling courses on your blog can be a successful way to make money online. The course itself should be relevant to your blog, and based on a topic that will benefit your audience. Although it may take time to create the course in the first instance, once completed, you can then repeatedly make money from the course each time you sell it.
However, like anything else truly worthwhile, apps require a significant investment of your time or money upfront. If you don't have the skills, then you have to hire someone who can assist you in creating a great app. But first you need to come up with an idea that will sell. Do the proper market research and analytics to come up with the right app.
Drive for Uber or Lyft: If you're in a locale where you can find Uber or Lyft (or even one of the many competitors around the world such as China's Didi), you could easily make a respectable income. The hours are flexible and you can work as you see fit, making it perfect even if you currently have full-time employment but are looking to make some money on the side. 
How much will you make? I think my best month with Google AdSense was almost $5,000 over the last ten years. That amazing month blew my mind since it was actually near the beginning of my blogging journey. When you go from making zero to $5,000 in a month, that will rock your world. For me, it also got me even more excited because I knew there were other ways to monetize.
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