Building an income portfolio is a function of a couple of things. First, look at your financial goal and then work backward. In this case, let's say an investor wants to generate $1,000 in passive income from three stocks in five years. The next step is to find three good stocks and then calculate how many shares to buy to generate that income. Theoretically it would take a smaller investment if we used a dividend reinvestment plan, but that complicates the math.

The three stocks are Realty Income (O 1.46%), STORE Capital (STOR) and Duke Energy (DUK 1.51%). I'll work through the math when discussing each one. Note that I am also choosing conservative names, which would be appropriate for an income investor. 

Picture of a calculator, a roll of money and a sticky note that says dividends.

Image source: Getty Images.

Triple-net lease REITs are highly stable income-generating businesses

Realty Income is a real estate investment trust (REIT) that focuses on single-tenant real estate properties. It is a Dividend Aristocrat, and has been a stalwart performer through thick and thin. It leases properties to tenants under long-term triple-net lease contracts. These contracts generally last a long time and push most of the operational costs on to the tenant. The stock is currently trading at about $70.60 and pays an annual dividend of $2.97. Over five years, the stock should pay a total of $14.85 in dividends, assuming no cuts or increases. To generate $333 in income you would need 22.5 shares, which would cost $1,589.

As a Dividend Aristocrat, the company has a long history of dividend increases, so chances are that the stock will generate more than $14.85 in dividends over the next five years.  During the COVID-19 pandemic, most REITs cut their dividends. Realty Income hiked its dividend three times in 2020. It should be a core holding in an income investor's portfolio. 

STORE Capital has a similar business model to Realty Income. It is a major holding of Warren Buffett's Berkshire Hathaway. Like Realty Income, it largely focuses on tenants that are somewhat more insulated from the business cycle than most. STORE's typical tenants include fast-food and casual dining restaurants, child education centers, supermarkets, retail, and some manufacturing. Like Realty Income, the company was able to raise its dividend during the COVID-19 pandemic. Its business model is highly conservative, and it does a deep dive into the financials of its tenants. The stock is trading at about $27.50 and pays $1.54 in annual dividends. Assuming no cuts or increases, that should build to $7.70 in dividends over the next five years. To get $333 in income you would need 43.3 shares at a cost of $1,195.

Regulated utilities are protected by the government

Duke Energy is a regulated utility, which is another favorite for income investors. Duke provides electricity and natural gas service to the Southeast and parts of the Midwest. Regulated utilities are often granted monopoly rights for a territory in exchange for letting the regulators determine what they are permitted to charge. This prevents the utility from price gouging, and it also ensures that it can earn a return without getting into financial distress. Utilities have historically been considered some of the safest stocks given that demand is pretty constant and they face little competition. Duke is currently trading at about $110.50 per share. Duke pays an annual dividend of $4.02, which would amount to $20.10 over five years. To generate $333 in income you would need 16.6 shares which would cost about $1,843

So, overall if you bought these three stocks, it would cost $4,626 to buy enough shares to generate $1,000 in income over the next five years. Given that these stocks have a history of dividend increases even during tough times, chances are the income would be more than $1,000.