Ants can build their nests in all sorts of different areas, such as walls, foundations, plant pots. They tend not to approach solid structures for their nests, hence don't often cause structural damage to buildings.
Ant nests can be dealt with by pouring boiling water into the nest, from the entrance. However, a DIY approach may not always be suitable, or effective, for getting rid of ants, and in this case, a professional pest controller is often the best option.
Ants can cause sever allergic reaction in certain individuals, especially with more aggressive variants like red ants.