I like the way you have listed the ways to earn extra income and was quite surprise that you did not make mention of network marketing, which is a way to make extra income without quitting your regular, though most people view mlm as a pyramid scheme but the real pyramid scheme is a regular 9 to 5, because you can only have one president of a company at any given time and network marketing business model to promote product that can be used is really cheap to join and can offer a substantial extra income or what do you think?
Building a smartphone or tablet app requires a fair amount of technical expertise, but it can pay off handsomely if successful. It doesn't have to be particularly complex or chock-full of features either; a simple one that solves a problem or is entertaining enough to attract users works fine. You never know what may suddenly become popular. For example, the minimalist game Flappy Bird was such a craze that at one point its developer was earning $50,000 dollars a day through in-app advertising. Of course, expecting a success like that is foolhardy, but one can always hope.
Real-estate crowdfunding ($9,600 a year): Once I sold my SF rental, it was natural to reinvest some of the proceeds into real-estate crowdfunding to keep sector exposure. I didn't invest a lot in some of my favorite real-estate investment trusts because I felt a rising interest-rate environment would be a stronger headwind for REITs. But if I could be more surgical with my real-estate investments by identifying specific investments in stronger employment-growth markets, I thought I could do better.
Taking Paid Surveys at Home: I was skeptical, at first, until my 17 year old son starting making money at home taking paid surveys. Companies desperately want your opinion, and they are willing to pay for it. The trick, of course, is knowing where to find the paid surveys that pay the best. One of the most popular and legitimate survey sites is Swagbucks. Not only can you make money taking surveys, but you can also make money by watching videos and even surfing the net. They also offer significant cash back for online shopping.

I prefer assets that make me a high return for the lowest amount of work possible (semi-passive involvement). And assets that pay me in several unique ways. Cash flow is only one way RE makes money for me. I also get principal reductions, appreciation, tax advantages (depreciation), and I control the rental increases on a yearly basis. Plus a majority of the capital is provided by the secondary market on 30 year fixed low interest rate debt.
When I started building my architecture-related business in 2008, I made my first dollar through advertising. I’d spent a lot of time and money building the site and getting traffic. Then one day I threw an ad on the site one day, and I made $1.18. Sure, I could find that much under my couch cushions—but that’s not the point! The point is that I was able to build something online, put an ad up, and make money without having to do anything. I learned it was possible, and it motivated me to move forward.

Just like any industry, there is good and not so good. The good part of passive income is that it can lead to multiple streams of revenue. Entrepreneurs understand more income sources means a more stable business and more room to grow. Implementing passive income strategies creates exciting possibilities and opportunities. Passive income sources allow me to have freedom and financial security in my life and business. I can spend my time traveling or writing, knowing that I'm stilling making income.


The reverse can also be expected unless the rents rise too.  This rental increase might occur if we imagine interest rates are rising because the economic environment is improving.  At present, it is widely expected that rates will rise ever so slowly over many years.  Indeed the US has been looking for the courage to do this over recent months and they may start rising there soon.
×