The “move in and live together arrangement”, (currently popular, and continuing to be so); which has developed over the last 20 years all around the United States of America): imported from Europe/France/ETC. which has been morally decadent for many years ...
It is a degrading way to live; and usually does not end in a successful marriage: the real truth being, It does not please God. It is being deliberately disobedient to His Word and instructions. There is a price to pay and it is costly. God is not mocked.
I live common law and God is OK with it; it’s the worrying about the speck in your brother’s eye, rather than the log in your own-crowd that irks Him the most. His son Jesus told me.