Mini-storage has been a terrific business for dozens of years… there was a time where it was a real gusher for real estate families, and organizations able to play on a mid-size scale, who got in early to buy odd properties cheap before there was pent-up demand from urbanization.
Mini-storage does share some of the good “wind at your back” attributes I describe throughout this Industrial Real Estate portion of this site, however the “barrier to entry” for competition is lower.
It’s easier now to add additional storage space to a local market due to good old ingenuity, economies of scale, experienced operators, and a financial appetite for larger players to finance larger projects. A good operator can afford to build multi-story units, aided by the very low parking requirements, and low traffic generation which lets a lot of square feet of storage building get put on lots which otherwise would get far less leasable space. (one day I’ll right a blog entry on the dynamics of parking, traffic generation, and land-use)