Sun in 7th house is not the most favourable position since this is originally the house of Libra ruled by Venus. If weak, this can cause a lot of legal problems in business and marriage, which could end up in a divorce, however, this can also make a person famous if well placed since this is the house of others and masses; the bright light of Sun will show your talent to everyone in the world.
The 7th house in Astrology shows that marriage, legal partnership (also includes business partnership), rules fame of personas its opposite of the 1st house which is self and 7th house is other people, house of masses, and it also involves sex and sexual relationship with the legal partner. (In Greek they say 5th and 8th house rules sex, but that’s not correct, 5th house rules romance, and 8th house, well, we’ll get to that next.) This is also a death-inflicting house (Marka House)Because dealing with marriage and its issues every day can kill anyone.
The 7th house in Vedic Astrology 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 from yourself The 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.
Sun in Astrology represents the soul. This can be read in the most flexible and general sense of the word. The word soul is used for the deepest and truest nature, forthe ultimate sense of identity, inspiration, and aspiration. Sun in 7th house signifies one's essential attributes - the sense of self, ego, self-esteem, a sense of purpose, and so on. Energies and conditions that arise from the Sun's placement in a horoscope, along with the influences that the Sun receives, will be experienced in life as deep, long-term trends and processes that impact one's life as a whole.
Note: The degree of auspiciousness and inauspiciousness will depend upon a complete analysis of the horoscope (birth-chart).