I don't believe in "live-in relationships" because to me, those involved are skating on their responsibilities. I'm old fashioned in thinking that if you want the sex and intimacy, marry.
I've known several people that have tried live-in relationships (homosexuals and heterosexuals) and living with their "partner" did nothing but end their relationship sooner.
When you live with someone, there are expectations of marriage, even if you're not married. I knew a couple that were together for over 5 years. They were great. Then they got married. Within months, they're relationship disintegrated.
I know that not everyone believes as I do. Many think it's a good thing to "test drive" the merchandise before you buy it. But it's just not biblical; and I've known far too many who've "tested" and have reaped the consequences.
I'm not saying it can't be done either. I know some that have done it and appear to be successful. However, they also hardly ever see each other and the man in the relationship has been unfaithful numerous times throughout their "live-in" arrangement.