Plainfield, Indiana, is a small town with an interesting story...

It sits in the middle of the state, at the center of a network of interstate highways and railroad mainlines. See the airport in the picture below? Plainfield is 10 minutes from Indianapolis International.

That patchwork of white squares, those are warehouse roofs. On average, each roof shelters around 500,000 square feet of storage space... that's about the same size as 10 football fields.

What's so special about Plainfield, Indiana?

Plainfield is the distribution center of the U.S. (Ask the Plainfield Chamber of Commerce. The chamber really makes this claim.) All in all, it is home to more than 40 warehouses, 22 million square feet of storage capacity, and almost 5,000 truck bays.

Plainfield: America's Distribution Center

Here's how it works: All our clothes, electronics, plastics, tools, textiles, furniture, and manufactured products come from China. First, goods are manufactured in China, loaded onto container ships, and sent to the Port of Long Beach in Los Angeles.

Once there, the containers are loaded onto trucks, which take Interstate 70 east across Nevada, Utah, Colorado, Kansas, Missouri, and Illinois to a warehouse near a town like Plainfield. The goods are unloaded there and prepared for distribution to stores in the major East Coast and Southeastern cities.

Wal-Mart, FedEx, UPS, Target, Walgreens, and most other major distributors all run their channels from hubs in the Midwest... and one of the genuine secrets of income investing is how much money you can make owning this Midwestern warehouse space.Plainfield just happens to be the most extreme example of this phenomenon. The reality is, you'll find heavy concentrations of warehouse properties throughout the Midwest... notably in Cincinnati, Louisville, Memphis, and Columbus.

Warehouse rents are nearly recession-proof. Tenants are huge companies that will always be able to pay the rent, even if the economy goes bad. Besides, even if a company falls on hard times, it'll fire people and cut costs long before it closes down the warehouse. So the warehouse owners will have plenty of time to line up new tenants.

Warehouse rents are low in volatility. Warehouses can be built faster and at lower cost than developments in other sectors, so reaction times are faster. Unlike the office and residential sectors, where new developments are built as speculations, in the warehouse sector, new space is built on demand.

Also, the people that rent warehouses aren't like college students who change apartments every other semester... warehouse tenants are stable, so your rental income is stable too.

Warehouses spin off lots of cash. First, industrial leases are usually "triple net." That means the tenant pays the operating and maintenance costs of running the property. The tenants pick up the utility bills, insurance costs, and property taxes... so the owners don't have to.

Also, it's always much cheaper to accommodate machinery and boxes instead of humans... warehouse owners don't need to provide tenants with carpets, cafeterias, artwork, parking lots, or expensive landscaping crews.

Warehouses have high occupancy rates. With a warehouse property, it's easy to make alterations to the space to adapt a warehouse to multiple tenants. In the industry, they say warehouses are "fungible.'' The long-term rate of warehouse property occupancy is 93%.

All this makes for very steady rent checks. Researching these industrial properties, I found warehouse investors can expect to earn around 8% a year in rent... and another 2-4% a year from property price inflation... all with very low risk.

The easiest way to get exposure to this kind of investment is through large industrial REITs, like Prologis (PLD). It's the biggest warehouse investor in the United States.