A second income could come in handy for all sorts of things, from booking a summer holiday to paying some unexpected bills. One option would be taking on extra work. But there is another way that millions of people already use, namely buying shares and earning dividends from them. Shareholding is one of my favourite passive income ideas. Why? It is passive. Companies like Unilever (LSE: ULVR) and Lloyds earn billions of pounds a year. By buying a little stake in them, some of that could come to me and help build a second income. Right now though, I do not own Lloyds shares – and have no plans to buy them. While the Black Horse Bank is solidly profitable, we have seen before how a deep economic downturn can hurt earnings at banks dramatically. Unilever, by contrast, is the sort of share I would happily buy now if I had spare cash to invest and wanted to start building a second income. I reckon demand for everyday items like shampoo and bleach is not only enormous, but likely to stay that way even when the economy wobbles. People do not stop washing their hair just because there is a...