1. Your relationship will probably end. An article on examiner.com states that 80% of shacking up relationships end before marriage or in divorce after marriage. So, it is 80/20 against you getting married, or staying married, to that person.
A relationship without commitment will not last. Marriage is the biggest commitment you can make in life. A legitimate marriage consists of a union between a man and woman who have made a covenant and commitment.
2. The dynamic of the relationship changes.
Most men argue: If you’re living with a woman and getting some of the “benefits” of marriage – sex, having someone to help around the house, sharing the bills – you can get lazy about taking the next step in your relationship.
3. Your children will be negatively affected.
To the parents who have children: a. Your kids are three times as likely to be expelled from school or get pregnant, b. they are five times more likely to live in poverty, and c. 22 times more likely to be incarcerated. All because you choose to live with someone you’re not married to. (Source: examiner.com)
4. The Bible considers shacking up the opposite of a legitimate marriage. Hebrews 13:4 reminds us that marriage is to be honored by all.
Shacking up is a violation of God's will for humanity and hence, will carry with it the painful consequences of sin.
Marriage, on the other hand, is designed to bring honor and blessings, not only to the couple, but to the church, community and the world.