One financial lesson I learned very quickly from both studying rich people and working with millionaires in Silicon Valley is that multiple sources of income are a MUST!The majority of my high school classmates didn’t go to college, and they hold unskilled or “blue-collar” jobs — and they only have one source of income.Now, that doesn’t mean they don’t work hard.I’d argue that some of my former classmates that lay flooring or even work in customer service or call centers have it much worse than I do in terms of dealing with difficult people daily.At some point though, you have to up-level your skills and get out of the weeds — having one source of income and making $40k a year with a family to support doesn’t leave much wiggle room for investing and creating additional income streams, and you can only work so many hours in the day.One of the easiest ways to generate additional income (in my opinion) is by investing in real estate.Many of my colleagues have at least one rental property in their portfolio as an additional income source.I don’t want to say real estate is 100% foolproof, but it doesn’t require coming up with a million-dollar business idea nor the time commitment and sweat that goes into running a company; it’s also fairly passive, allowing you to earn income while you sleep.If you like the idea of investing in real estate but don’t have the down payment or you don’t want the responsibility of owning property, you can check out my post on how I invest in real estate.Lastly, if real estate isn’t of interest or you’re in a stage of your career where you need to up-level your skills to generate additional income, the internet is a great place to start.Pick something you like,…