Why can't we just live together?

Yahoo picked up this recent topic from a Beliefnet.com advice column written by Dr. Renita Williams. The seeker of advice writes:

Dear Renita,

I was raised Catholic and attended Catholic school most of my life. I have always believed in God. I have taken classes on both the Old and New Testament, recently becoming a more committed Christian. But there is one question I have not found an answer to -- and I know many Christians consider it wrong -- so please guide me to a place in the Bible that addresses this issue.

My boyfriend and I have been together for 5 1/2 years and have lived together all but one of those years. We are very committed to one another and plan on marrying. We have put off getting married for a couple reasons. One, with me back in school we are living on a very limited income and can not afford rings or a wedding now, as we both have some debt we are working to pay off. I know that Christians feel it is wrong to live together before marriage. But it just doesn’t seem feasible for the two of us to maintain two separate residences -- and after already living together, it seems silly to divide up now. Where in the Bible can I find a basis for this belief held by so many?

Cohabitating and Confused

My own immediate thoughts are that it only takes $41 dollars to get a marriage license in Texas and just few more dollars to buy rings made out of genuine metal (which can be replaced with something finer later on). That's all it really costs to get married if you go to a priest rather than a Justice of the Peace and if you are willing to see marriage as a sacrament rather than a circus. We could make it a very traditional wedding for barely any cost at all. And if a couple has trouble paying for a license and rings, I'd much rather cover that with my discretionary fund than see them jeopardize their chances for a strong and lasting union or continue to settle for a counterfeit to marriage indefinitely.

Rita gives a thoughtful response to "Cohabitating and Confused" in her advice column here. I would only add that it should be remembered that marriage is essentially a vocation to holiness. What wounds holiness also wounds marriage.