The biggest and most obvious draw to purchasing a self storage facility is the fact that a person won't have to deal with cleaning apartments or houses, toilet and plumbing issues, and other types of problems that may arise with owning properties that are used for residential (and even business) purposes.
Because most self storage units are made out of the metal, they are relatively easy to clean out and prepare for the next tenant after one leaves. Furthermore, if a storage unit is listed as abandoned due to non-payment, when they are auctioned off, the auction winner has to clean out the unit.
There are usually less employment costs when it comes to properly staffing a self storage facility as well. In most cases (depending on the size of the property), only one or two employees are needed at open business hours during the day. With proper gates and other security measures, a self storage facility can operate fairly independently, without the extra cost of employees that may be needed for other types of businesses.
There are other benefits of owning and operating a self storage businesses, but these are main draws which convince potential investors that self storage is a viable business and real estate investment.