I'm interested in building an in-ground or above-ground storm shelter. What would be the approximate cost of one that can accommodate four people? And ultimately, is it cheaper to pay someone to build and install it rather than do it myself?
A storm shelter is a great idea, but for maximum protection, I'd advise against building one yourself. Not only will a manufactured, premade, ready-to-go shelter most likely protect better than anything the average person can construct on their own, it will likely be less expensive than doing it yourself, too.
Companies like Valley Storm Shelters and Lifesaver manufacture storm shelters day in and day out - and many manufacturers will deliver your shelter to your home, as well. Consider putting DIY effort into hooking up shelter utilities like lights and insulation.