Ants have a very good sense of smell and hate the smell of cinnamon. Add half a teaspoon of cinnamon oil to a cup of water. Soak some cotton wool in it and rub this near areas where the ants live. Repeat the procedure until the ants have gone. Put some cinnamon sticks outside, in particular near the door, on window sills and near other entrances. You can also put the cinnamon oil in a spray bottle and use it on any ants you encounter.
Vinegar is another thing ants hate. That is good news because it makes for a cheap deterrent. Fill a spray bottle with equal parts vinegar and water. Add a bit of scented oil such as lemon, which is another scent they hate. Shake well before use and spray around all possible entry points. Do this several times a day until the ants will disappear completely.
Borax is a natural mineral that is a compound of most pesticides. Borax is sold as a powder or as colorless crystal salt. You can buy it in some supermarkets or at the pharmacy. All you will need is a cup of warm water, half a cup of sugar, two dessert spoons of Borax and some cotton wool. Combine the ingredients and soak the cotton wool balls in the Borax mixture. Then place the cotton wool balls wherever you like, for instance on ledges that ants often use to come in.