Ketu in 7th house is the worst position unless you have no desire for marriage. Ketu also gives lots of legal problems and insults from the public. People with this Ketu usually have an odd personality.
The 7th house is opposite the 1st. The act of marriage takes us as far away as possible from who we are by ourselves: it is an agreement to live with, to accept, to love, and to support someone who may be totally different than yourself. Marriage brings about relations with the in-laws and people in general. Marriage is also likely to bring travel, as at least part of the family is not under the same roof The lower part of the belly (the region below the navel according to Parashara) is next in line. This includes the large, intestines and kidneys. Libra corresponds to the 7th house. Movable, ruled by Shukra (Venus), it reinforces the significations of marriage, social interactions, and travel
Ketu is also an unsteady and sometimes treacherous force, but its qualities are more of an abstract, inward nature, in contrast to Rahu who is more concerned with outward, worldly matters. Ketu can bring hindrance and obstacles in the physical realm of life but indicates sparks of intelligence and brilliance of the mind. The above significations are extremely important to know by heart. You should memorize them, and use them often to remind yourself of the essential nature of the Grahas.
Note: The degree of auspiciousness and inauspiciousness will depend upon a complete analysis of the horoscope (birth-chart).