"It is better to have a permanent income than to be fascinating." - Oscar Wilde.
What would you do if you lost your job? Do you have any additional monies coming in from other types of income that could help you get by until you get a new job? I used to work in the resource sector, and if you know anyone who works in that sector, you've probably heard that it goes through violent boom and bust cycles. A job and career this year does not guarantee a job and career the following year, so it became a high priority for us to create multiple income streams in case I found myself without employment. You've also probably heard the phrase "Don't put your eggs in one basket" right? Well, in my mind if you only have one type of income, you essentially have your income eggs in only one basket. For example, if your employment income is discontinued for some reason such as an injury or a layoff, you may have nothing to fall back on.
I would think single people, or couples who both work in the same industry, are particularly at risk to this scenario. If their jobs disappear and the household income is so concentrated in one sector, it can have significant impact on your savings if employment income is your only source of income and it goes away. Having a second or third income stream is the akin to building up addition skill-sets that you can use when the need comes, or separate income you can use to fund your retirement when you stop working. Some examples of second income streams are: investment income, a second job, trading income, a home or personal business, freelancing, royalties from music or a book that you produce, blogging income, income-producing real estate, pensions or annuities that you buy and so on.
Developing multiple income streams is typically not something you can do overnight. People who take on this strategy often go to work during the day, and then come home at night after toiling away in teh salt mines and then do further work or research in their time off. There is no shortcut or get-rich-quick strategy that works, so don't expect the payoff to occur until well into the future. Any extra money you generate could help you fund your current lifestyle, your retirement savings, or can be reinvested to make even more income in the future. If your secondary sources of income become great enough, you can choose to work part-time instead of full-time.... or possibly not at all.
There are lots of online sources giving you advice on how to start new income streams, but before diving into any of them, I would advise you to choose something that you are already keen on. If you are into sports perhaps try refereeing high-school games. If you like to write, try writing an ebook on a topic you enjoy. For me, I chose to build passive dividend investment income and then juice that up with some conservative income-producing options-trading strategies. Money management and financial strategy is something I've been pretty keen on since I was in high school, so these types of income were right up my alley. Learning these strategies involved study, study and more study early on, but eventually they became like a second language.
Over time our second and third income streams have increased significantly and have contributed to our financial confidence and security. We've been working on these streams of income for some time now, to the point where we can see ourselves being able to live a spartan lifestyle solely on them within the next 5-10 years if we needed to. Our trek to financial independence has certainly gotten a boost from having these additional incomes. Having multiple income streams has given us significant flexibility and control over our finances as the income continues to grow.