One woman wrote: I wish I could tell every young adult that you truly will reap what you sow. Cohabitation (live-in relationship) may seem wonderful initially, but eventually it creates more problems than you can imagine.
I lived with my boyfriend for two years before we got married. I knew I was breaking my parents’ hearts, as well as my Heavenly Father’s heart! My boyfriend was not a Christian, but I figured I could change him if we moved in together.
The “this-is-yours, that-is-mine” mentality that enabled us to “successfully” live together completely unraveled once we got married. We had become too separate and too selfish, making it nearly impossible to become “one flesh.” The honeymoon was over before the wedding day ever arrived. - Josh McDowell’s book: ‘Right from Wrong.’
“Cohabitation is a near occasion of sin, gives scandal to others, provides a cover for fornication and involves the couple living as if married when they are not. We can't assume couples placed in such tempting circumstances would stay chaste.
You don't need to live with someone to know whether they get on your nerves or not, that is as far as I am concerned a weak excuse used by people who want to enjoy the married lifestyle without making the commitment and sacrifices of actually been married.
And once they are enjoying the married lifestyle without actually getting married, they very often quickly come to the conclusion that there is no need to actually ever get married.” (Forum on Cohabitation).
Heb 13:4 says: “Let marriage be held every way in honor, and the bed be undefiled; for fornicators and adulterers will God judge.”