A quick search reveals that as of this writing, 982 stocks listed on the NASDAQ or NYSE have dividend yields of 5% or more per year. However, a high dividend all by itself doesn't make a stock a good investment -- it's far better to focus on companies whose dividends grow over time, have relatively safe business models, and have the potential to generate share price appreciation in addition to income.

Real estate investment trusts (REITs) can be a good place to find all of the above. Specifically, here are two excellent candidates -- Iron Mountain (NYSE:IRM) and Medical Properties Trust (NYSE:MPW) -- that are good buys right now.

Specialized storage facilities

Iron Mountain owns and operates information storage facilities and provides information protection, storage, and records management services to more than 170,000 customers worldwide, none of whom account for more than 1% of the company's revenue. The company currently operates 1,100 facilities in 41 countries, and 94% of the Fortune 1000 are among Iron Mountain's customers.

Image source: Flickr user Drew from Zhrodague.

The company has produced 26 consecutive years of revenue growth and has some pretty ambitious expansion plans going forward, including aggressive expansion into emerging markets. As of the first quarter of 2016, emerging markets made up 15% of Iron Mountain's revenue, which the company hopes to increase to 20% by 2020. This is in addition to planned expansion in the company's "adjacent businesses" such as data centers and art storage, and ongoing cost-cutting initiatives.

Another reason I like Iron Mountain is that storage facilities may sound boring, but they can be one of the most profitable types of real estate to operate. With lower ongoing costs than most other real estate, storage facilities don't need high occupancy to make money, tenant retention is high, and turnover expenses are low. In fact, Iron Mountain operates at a strong gross profit margin of 76.8%.

Iron Mountain currently pays a $1.94 annual dividend, which translates to a 5.3% yield. The company has stated its goal of a $2.18 payout by 2018, and if it continues to achieve its growth targets, I don't foresee this to be a problem.

Healthcare real estate is cheap right now

As a group, REITs focused on healthcare properties are trading for extremely low valuations, and Medical Properties Trust is one of my favorites. The company specializes in hospital properties, and in fact is the fourth-largest owner of for-profit hospital beds in the country, with 204 properties.

Aside from the cheap valuation, which I'll get to in a second, healthcare real estate should be a high-growth market over the next several decades. The senior citizen (65vand older) population in the U.S. is expected to almost double by 2050, and healthcare costs have been rising quicker than other expenditures.

As far as valuation goes, funds from operations, or FFO, is the best metric to use when valuing REITs (as opposed to earnings per share). Here's an explanation, but let's just say for now that FFO is the "earnings" of the REIT world. Medical Properties Trust is trading for $14.70 per share as of this writing and is projecting 2016 FFO in the range of $1.29 to $1.33 per share. So, using the midpoint of this guidance, this corresponds to a price-to-FFO multiple of 11.2. Compare that to other leading REITs such as Realty Income (20.9 times 2016 FFO) or Equity Residential (22.3). Even my other high-dividend favorite, Iron Mountain, trades for 17.1 times projected FFO.

Now, it's worth mentioning that the healthcare REIT is cheap because of a higher perceived risk. Many healthcare facility operators are in financial trouble, and there is significant uncertainty about the future of healthcare spending in America. However, I feel the risks are priced in and then some for Medical Properties Trust, and the 6.1% dividend yield should provide a strong, growing stream of income for decades to come.

Invest with the long term in mind, and be patient

As a final thought, I want to emphasize that these stocks are best-suited for the long-term investor, which I'll define as someone with a five-year investment timeframe or more. The entire point of REITs like these is to create a growing income stream and take advantage of the long-term price appreciation of the underlying properties.

There are certainly some factors that could hurt both stocks' prices on a short-term basis. For one thing, REITs are often vulnerable to interest rate hikes since it makes borrowing more expensive and also makes safer fixed-income investments more appealing. Or, another recession could occur and lead to a decline in property values. However, I'm confident that over time, these two stocks have nowhere to go but up -- and, you'll get a pretty nice income stream along the way.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.