​Udemy is an online platform that lets its user take video courses on a wide array of subjects. Instead of being a consumer on Udemy you can instead be a producer, create your own video course, and allow users to purchase it. This is a fantastic option if you are highly knowledgeable in a specific subject matter. This can also be a great way to turn traditional tutoring into a passive income stream!
One of the most appealing options, particularly for millennials, would be #12 on your list (create a Blog/Youtube channel). The videos can be about anything that interests you, from your daily makeup routine (with affiliate links to the products you use), recipes (what you eat each day) or as you mention, instructional videos (again with affiliate links to the products you use). Once you gain a large following and viewership, you can earn via Adsense on YouTube.
Thank you for sharing your article! You did a great job saving and putting your money to work for you. Like you, I share the same financial dream of having 150-200k in passive income and traveling the world stress-free! :) Right now I’m saving about 80-90% of my active income and put it toward ETF funds and value growth stocks because I’m seeking capital appreciation. And I can tolerate a lot of risks because I’m still in my early 20’s. By the time I reach 30 something I’ll start looking into blue chips stocks that pay dividends and REIT. So I want to be where you are by that time lol. Anyways, that the plan and I’m sticking to it. Good luck on achieving your financial dream!
Developing passive income is different. With the exception of one of my passive income streams (cryptocurrency mining), all of the others require real, hard work. Truly, I understand the barriers for people getting into building alternative income streams. I would say that most people WANT passive income, but truly aren’t willing to put in the blood, sweat, and tears to make it happen.

Do you have stuff in your basement, attic or garage that's collecting dust? If you do, pack up the SUV or car and kids and go to a flea market. You could make a couple of hundred, even thousands, of dollars, depending on what you're selling. You'll want to go to flea markets every weekend or at least every other weekend. Make an event out of it, and show your kids how easy it is to earn money selling their stuff.
Investing in rental properties: Another form of real estate investment, rental investments (i.e. becoming a landlord) could steer you down the passive income path of steady monthly rent checks that you can use to pay off a mortgage loan on the rental property. After the mortgage is paid off, those monthly checks go right into your bank account -- potentially for years to come. 

Lending Club is a platform where you can lend your money to other people. You’re the bank. Each note is only $25, so you can invest $1,000 and lend money to 40 people. There are many grades of loan (from safest to riskiest) and investors earn, on average, between 5% and 7% annualized returns. For more information, check out Investing and Making Money with Lending Club Peer-to-Peer Lending and my real money Lending Club Portfolio.

You know the fantasy: write some ebook (or better yet, hire freelancers in Mumbai to research and write it for you at $.20/word!) on some niche topic, set up AdWords and Facebook campaigns targeted to the right keywords (you can hire those Mumbai guys to do your keyword research too), put up a cheap landing page (with copy written by... guess who!), press "Go!" on the PPC campaign, and voilà. . . just wait for the money to roll in while you sleep!
When you buy a turn-key rental property you are saving a lot of time and work, by letting the turn-key company complete the repairs, find the property and manage the property. You are giving up equity in the property over buying one yourself, because you aren’t doing any of the work. You have to decide if the time you save is worth the equity you give up. Typical returns I have seen on turn-key properties have been in the 10 percent range.

Whether you take a “distribution” (aka free-cash-flow) in the form of a dividend, interest payment, capital gain, maturing ladder of a CD, etc, you are still taking the same amount of cash out of your portfolio. Don’t fall for the trap of sub optimizing your overall portfolio’s performance because your chasing some unimportant trait called “income”.
Get paid to take surveys at home by signing up with one or more survey websites. All you do is answer questions and voilà, you get paid. Another way to earn extra income is to participate in focus groups. Companies hire focus groups as a way to test out a new product before it hits the market. Why? Because they need to make sure it will make money; they want a high return on their investment. Surveys and focus groups may not make you a millionaire overnight, but you can earn hundreds of dollars each month by giving your opinion on products and services.

Though it can take a while to build up enough cash to put a 20% down payment on an investment property (the typical lender minimum), they can snowball fairly quickly. The key here is to correctly project income and expenses in order to calculate cash flow (the free cash you can put in your pocket after all associated property expenses have been paid). However you have to be sure to include the cost of a property manager in your calculations unless you want to manage the property yourself. Even with a property manager, you may be required to make large repair decisions every now and then – so while this is not a 100% passive activity, you are not directly trading your time for money like traditional employment.
Another way to generate passive income is to invest and be a silent partner in a business. This is very risky, but with risk comes the potential for high returns. For example, several years ago both Lyft and Uber were looking for private investors to invest in their companies. Today, they are worth billions - but you as an investor would only reap that benefit if they go public via an IPO, or get acquired. So, it's risky.
If you’ve ever thought to yourself, “I wish there was a product that did this,” then invent it! Create a product, medical or otherwise, and sell it as a company or get royalties for it. It’s not impossible to figure out, I have many friends who have taken a concept to market. Don’t overlook an invention as a fantastic means of attaining passive income.