The United States Conference of Catholic Bishops put together this reference material about marriage preparation for cohabitating couples.
I found it interesting to read and felt more at ease after going through it. I encourage cohabitating couples or those considering it to give it a read. I'd like to point out that their statistics don't seem to totally make sense to me at times, but I was comforted to read the specific concerns of priests and how they are being instructed to handle it.
Sometimes it seems the Catholic Church shuns the issue without really explaining their specific concerns. I'm not sure how I feel about everything said in this article, but I am glad I was able to read more of an explanation.
I've noticed some of the MGs offering advice on some topics in previous posts -- I'd also like to hear any of your thoughts about this material.
http://www.usccb.org/laity/marriage/cohabiting.shtml