According to Freda Edis in her The God Between: A Study of Astrological Mercury (Contemporary Astrology) :
“In the second house, Mercury indicates a mind concerned with securing personal resources which may be both material and psychological. The possession of clear values and a personal sense of worth are important to people with this placement. At heart, they often feel the need for the security which comes with an intelligent recognition of a sense of values and self-esteem, though they might not always be aware of it. Often the trait takes the form of a pride of ownership. Attachment to physical objects, people or inner desires and ways of thinking is characteristic.
So people with this placement may need to learn very consciously how to appreciate their worth without being either possessive or smothering to excess. They are capable of reaching a realization of the worth of their inner system of values and the way in which they use these in their dealings with others. At the same time, it is possible for them to combine this inner awareness with a desire for material and intellectual security and resources. Coming to a satisfactory appreciation of their possessions without feeling that they themselves are owned by them, or by their own attitudes of mind, may help them considerably.
Choice-making between things of value might be a function which would benefit people with Mercury in the second house. Where there is little discrimination between values, it is often because people are afraid to let go of what they once possessed, even when it becomes redundant. Fear of the consequences of making the wrong choice is a factor involved here."