You can make money whichever way floats your boat. I got a lot of slack in this post for trading forex, but I live in one country, and need currency from three other countries where I own property and travel to often, so when one currency is cheap, I do take advantage of fluctuations. It may not be your thing, but the important part is that you have more than one source of income.
In equity valuation, residual income represents an economic earnings stream and valuation method for estimating the intrinsic value of a company's common stock. The residual income valuation model values a company as the sum of book value and the present value of expected future residual income. Residual income attempts to measure economic profit, which is the profit remaining after the deduction of opportunity costs for all sources of capital.