Building a portfolio of high-yield dividend stocks and reinvesting the payments can be one of the best ways to put your money to work and build wealth over the long term. Not every stock that offers a big payout will prove to be a hit, so it's important to focus in on companies that offer yields and risk profiles that fall within your desired range. 

For investors seeking big dividends, Welltower (NYSE:WELL), AT&T (NYSE:T), and IBM (NYSE:IBM) are three stocks that offer yields above 4% and have business and valuation profiles that could appeal to a variety of investors. Welltower looks like a safe, dependable play in real estate properties that's set to benefit from demographic trends, AT&T has struggled over the last decade but still looks pretty sturdy and has a great dividend, and IBM stock now looks like a riskier play but could have a big payoff if its recent massive acquisition is successful. 

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Welltower

Welltower is a real estate investment trust (REIT) that specializes in healthcare and senior-living properties. As a REIT, the company generates its revenue from rental properties and abides by a specific set of regulations. Some of those extra regulations work in shareholders' favor, such as the requirement to pass along at least 90% of taxable income in the form of cash dividends.

That means that unless profits take a hit, shareholders can feel safe that the company won't slash its payout beyond a certain point. While many REITs cut their dividend on the heels of the 2008 financial crisis, Welltower maintained its payout. It's paid a dividend for 48 years running, and its overall returned-income component continues to look appealing. 

Welltower sports a 4.1% dividend yield, and it's unlikely to cut it anytime soon. While the company didn't deliver a payout increase last year -- ending its 15-year streak of annual dividend growth -- the REIT looks well positioned to continue growing earnings in the coming decades.

Medical care and senior-living centers face little risk of disruption and will likely see strong demand increases. The United Health Foundation reports that nearly one in eight Americans are currently above the age of 65, and projects that figure will rise to one in five by 2040. These demographic tailwinds should ensure that Welltower's properties remain in high demand and allow it to continue cutting big checks to shareholders.

AT&T

AT&T's business has been sandbagged by declining subscribers for its DIRECTV satellite television business and a competitive mobile-wireless market that has elevated service standards and limited pricing power. This has translated to anemic sales and earnings growth and caused the company's share price to dip roughly 7% over the last five years -- a stretch that has also played host to a big rally for the broader market. But AT&T remains a great destination for investors seeking large and dependable dividends, and its depressed valuation suggests real comeback potential if some of its growth initiatives are successful.

The telecom giant's stock currently yields roughly 6%, has reasonable payout ratios, and boasts a 35-year streak of annual payout growth. Even with the company directing some of its free cash flow to paying down its big debt load, it should be able to continue delivering small but steady payout hikes while investing to prepare new growth engines.

The company's core wireless business continues to look strong even if it's not in a high-growth phase, and long-term technology tailwinds stemming from 5G network technology and the Internet of Things could be substantial catalysts. Factor in the potential to benefit from increasing demand for entertainment content with its Time Warner division, and leverage tie-in opportunities with its mobile wireless service and DIRECTV packages, and AT&T stock has ways to deliver wins beyond its great dividend. 

IBM

IBM has historically been thought of as a pretty conservative investment. But with the company valued at roughly $127 billion and having recently acquired Red Hat for $34 billion, it's clear that IBM has moved into riskier territory.

That said, the business still trades at reasonable multiples (roughly 10 times this year's expected earnings) and packs a big yield at roughly 4.5%. Investors who aren't put off by a riskier IBM and are willing to bet on the Red Hat buy bolstering the company's position in cloud services have the potential to record stock gains in addition to big dividend payments if things go well.

With Big Blue's legacy hardware and related services business looking like it will slowly continue to atrophy, that puts a lot of pressure on the company's internal growth initiatives and its big acquisition to get things back on the right track. But it still has some time to work things out, and its dividend looks pretty safe. The company is still generating strong free cash flow, putting up roughly $11.74 billion over the trailing 12-month period -- working out to $12.92 per share. That means that the company's dividend payout comes in at half of free cash flow, a safe level that puts the company in good position to maintain its payout and continue nudging it higher.