The 7th house is an angular house, known as the descendant and the house of your partner. This house is home to the cardinal sign Libra ruled by Venus and is the masculine expression of that planet. The element closely attributed to this house is Air. This house is related to social interactions. Because the 7th house shares its axis with the 1st house communication is one on one. The seventh house shows your one or one relationships, business partners, contracts. Being 10th from the 10th house, the 7th house represents laws your career, and the legacy created with someone else as well as marriage. Because, this is an air house ruled by Venus this house, through logic, is how you use your values, voice, and possessions to create a harmonious existence.
When there are planets in the seventh house, they take on Libra qualities. It is also like having that planet conjunct Venus. This is the masculine aspect of Venus so values, money, possessions are sought outwardly through others. If there are personal planets in this house it has a powerful influence on your personal life be it Sun your ego, Moon your emotion, Mercury how you communicate and your peers, Venus your values and interpersonal relationships, and Mars what you put your energy towards.
With the Sun in this spot the ego and what you want personally has to take a set. This is the house about creating harmony with someone else through compromise in order to get the objective goal of the partnership. So your conscious personality has to water down a bit, becoming passive or deceiving to obtain that harmony. Moon in this house has someone with there emotions dependent on their relationships with others, or instead of wearing your heart on your sleeves as in the 1st house, those you are around on a one on one base will seem emotional. Thus, relationships, business dealings etc. seem to ebb and flow like the tide. You have an intuitive understanding of relationships.
With Mercury here, you like jokes with your partner. They should be quick-witted with a sense of humor. You think about relationships, and enjoy more than one relationship at a time. Not always on the same levels meaning you have a romantic sexual relationship, and you are curious about having a no sexual romantic relationship or what have you. With Mercury here, you tend to analyze relationships, business dealings with others to better understand them. Your words and how you communicate will add to your ability to gain some sort of benefits from others. Not in the same way as the 8th house, the 7th house is a precursor to the 8th. Emotional involvement is not something that comes to mind this is the individual meeting others on the detached and logical level.
This is the house of Venus. You value harmony, socially accepted and refined beauty, relating to others or your environment in some way. You know how to be in a relationship and how to have it benefit you in the long run. Mars in this house is the go-getter when it comes to relationships. But Mars has to refine its raw energy to fit in Venusian houses. This is not the best placement for this planet but, Mars will make it work when it comes to things of this house. You will want to go after relationships and may have many partners who want to dominate relationships. You will have to stick up for yourself when it comes to others.