If you have a basement, you may not need an actual storm shelter. You live in Alabama, right? It's hard to get an F4 or F5 tornado in Alabama...so I would think a well-constructed basement (good ceiling) would be fine. If you could possibly clear out an area from sharp objects, glass, overhead objects, etc.....that would be going a long way. If a shelter isn't terribly expensive, then you could always go that route - but if they are, you may want to just consider your basement. The floor of a house isn't going to be ripped off in an F3.