When you are buying a house in a tornado-prone area, there are a lot of things that you need to look for. You want to make sure that you do everything that you can to make sure that you are safe in your new house.
One thing you are going to want to check is if there is a cellar or safe room in your prospective house. A cellar or storm cellar underground will be more protected from the wind of a tornado. Since there are generally no windows and exterior walls are all supported by earth, the walls are more secure than anything else. A safe room is a room that has been specifically designed to go through a tornado safely. The rooms are generally completely interior rooms with reinforced walls. Those reinforcements can include additional beams and walls made of metal or cement. Generally these only show up in newer builds and may double as a large closet, but they can be retrofitted in older homes.
Another thing that you should look for is reinforced connectors. These connectors will run all the way down from your roof to your foundation. They act as extra tie downs and will give your roof and walls the extra support that they need to make it through a tornado. The winds in a tornado can get up and under the roof, lifting it up. As the roof fails, the walls will start to fail as well. But having the additional connectors that connect it to the foundation makes it harder for the wind to lift the roof and destroy it.
Something else you may want to look for is hardened walls. These walls would have things like extra studs, metal reinforcing, or even cement reinforcing placed in them. The hardened walls resist the wind, as well as helping to resist the debris that can be flung around in a tornado. Even small pieces of debris being flung around at 100+ mph can cause some serious damage to your walls and possibly destroy your house's structural integrity.
If you are buying a house in a tornado-prone area, you want to make sure that you are looking for things that will keep you safe. You can make sure that you ask real estate agents to help you find houses that will fit your needs and desires. After all, a safe home should meet your other needs as well.