How One Millennial Made More Than $60,000 in 30 Days Without a Full-Time JobYou might not think of it as a lucrative source of income, but teaching online courses can result in some significant income.

Before last year 25-year-old entrepreneur Nick Walter of Provo, Utah, had never heard of the Udemy online-course platform until a friend introduced him to it. An iOS developer, he quickly figured out how to use the platform to offer his first course and then figured out how to do something really ingenius this summer.

Walter, whom I recently interviewed, set up aKickstarter campaignfor his class "How to Make a Freaking iPhone App,"on Aug. 12 and in effect presold his $199 course for just $29.His initial goal was to raise $1,000 for the 30-day launch, but he ended up making $66,533 in just 30 days without having a full-time job.

When Walter first checked out the Udemy platform last year, he saw how all these instructors were making a killing,teachingwhat they knew. He knew he had to put his hat in the ring. So he did.

He had just attended an Apple development conference in 2013 where a new programming language called Swift was introduced. He thought this all amounted to a unique opportunity for him to do some intense learning while teaching at the same time.

Says Walter: "I knew that if I was one of the first ones to create a class on it, it would gain a lot of traction." And that's how it turned out. Over the course of a single week all he did was eat, sleep and learn Swift. By the week's end, he had made 50 short videos and promptly uploaded them to Udemy.com.

To date, his first course, "Swift – Learn Apple's New Programming Language Step by Step,"has had more than 8,000 students enrolled. "I was successful with my iPhone app class because of my Apple Swift course," he tells me. "I was able to leverage some of the students from my first class to want to join my second one."

Another success story involves Nick Loper ofSideHustleNation.com.Earlier this year the Livermore, Calif., resident wrote a Kindle book,Work Smarter, which generated $1,400 over 30 days of sales on Amazon. Because he kept on being asked the same question from readers about how they could replicate his success, he decided to teach a course -- on you guessed it, Udemy.com.

In his online course, "Kindle Launch Plan: $1400 in 30 Days & an Amazon Bestseller," Loper teaches his students how to build a foundation on Amazon and then successfully launch a book even if an author doesn't yet have a large audience of fans.

Now I hope you're beginning to see what teaching what you already know can do for your bottom line. Here are three great ways to capitalize on your unfair advantage (teaching what you already know):

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1. Udemy

Based in San Francisco,Udemyoffers more than 20,000 courses in every topic or genre you could possibly think of. The best thing is that teachers get to set their own prices, come up with their own topics and if they market a course, they keep 100 percent of the profit.

If Udemy does the marketing and brings in the students, the instructor keeps 50 percent of the profits. An instructor on average makes $7,000 on Udemy and 96 percent of instructors do achieve sales,according to the site.

Related:15 Free Online Learning Sites Every Entrepreneur Should Visit

2. Skillshare

Online learning communitySkillsharelets people take some amazing classes for free (althoughupgradesare available for pay). It also lets individuals teach on the platform and earn side income based on what they already know, love or are passionate about.

Do you have expertise in design, gaming or programming? Then teach a course in one of these areas. Skillshare has more than 750,000 students, 35,000 student projects and has paid its teachers more than $3 million,according to its site. An instructor on average makes more than$3,500. So what are you waiting for?

3. Dabble

If you're more of the hands-on type when it comes to teaching, thenDabble.cois the platform for you. You sign up to teach classes in your own community. You can teach in a coffee shop or restaurant -- you name it. Classes can be taught by anyone (which means you). You can attend a class, teach one or host a class and have someone else do the teaching.

So now that you have the tools, it's time to start building. If you're feeling a little hesitant, I'll be sharing my insights about this very topic in an upcoming course I've titled"Teach Online: How to Create Side Hustle Income Leveraging Your Existing Skills."

Let me know about your teaching successes in the comments section.

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