I know of two websites that can help you see the current inventory of storage facilities throughout the country.
They don’t always account for everything (sometimes there are lesser known facilities that don’t show up in their database), but you’ll see about 90% of what’s out there.
One of them is RadiusPlus, and the other is StorTrack, and they both do a similar thing.
Last I heard, the national average is about 7-8 square feet of storage space per person. So, if you see that the supply of self-storage around your location is less than this, there’s probably enough demand to support a new facility or expanding an existing one. If the supply is higher than this, it could still work, but it may take longer to fill up.
These websites will let you pick a location and then draw a radius around it (3 miles, 5 miles, 7 miles, 10 miles… it varies, depending on how rural your location is and how dense the population is). For rural locations, you’ll want to use a larger radius, like 7-10 miles, for urban areas, you’ll want to use a smaller one, like 3-5 miles.
Whatever radius you pick, it will show you how many sq ft of self storage there is per capita around your chosen location.
You can create an account and start searching for areas. It will show you what other facilities are nearby, how much square footage they have, what kind of storage they have, and more. I think RadiusPlus will give you a small number of free searches before you have to start paying for it. I don’t recall how StorTrack works because I’m currently paying monthly for that one.
They’re both awesome tools that deliver very important information for making these decisions.