If you describe someone as footloose, you mean that they have no responsibilities or commitments, and are therefore free to do what they want and go where they want. People that are single tend to be more footloose
If you describe someone as footloose and fancy-free, you mean that they are not married or in a similar relationship, and you therefore consider them to have very few responsibilities or commitments. free to do exactly what you want because you have no responsibilities, for example when you are not married or do not have children