Wanted to revisit this issue. Since my original post I have 7 co-habitating couples out of 18 total units in my building. Many of these couples have children out of wedlock. I still have a bad conscience renting to such couples. Sure, many posters have mentioned that I am not responsible what my tenants do behind closed doors. It just seems that the moral fiber of our society is in shambles as it seems common that a great majority of couples live together before marriage, and many such couples forego marriage all together.
As has been mentioned before, you are not allowed to discriminate based on marital status or sexual preference (I say this, in the event that you have some homosexual couples renting from you)
First of all, if you want to be absolutely clear of the problem, the only choice you would have is to sell the property and get out of the landlord business. But, based upon the scan of the thread, it does not appear that this is an option you are willing or able to take. So I would study up a little bit on moral theology.
Specifically, I would study up on the subject of “cooperation with evil.”
Since you obviously do not approve of the actions of these cohabiting couples, your cooperation with evil is not “formal cooperation”
However, since the action you take of renting the flats out is related to the couples to live in a state of sin (a conjugal relationship outside of marriage), it would still be material cooperation. If your cooperation was a necessary part of this evil act the cooperation would be “immediate” (in other words, would they be able have that conjugal relationship if you didn’t rent to them?). If you judge that it would, then you are just as responsible as if you matched the couple up and encouraged them to move in together.
If your cooperation is more peripheral (in other words, the rental of the apartment facilitates their relationship but is not essential to it happening), then your cooperation would be considered “mediate” cooperation. You don’t intend for the result to happen, it could happen without what you provide (even if they didn’t live together, they’d still be able to fornicate), but you’re still involved. Most moral theologians that I am familiar with would say that your culpability in that circumstance is very limited.
One question: are you required to sign leases with all of the names of the residents on the lease? Or can you, without running afoul of the law, have a policy of leasing a unit to a single name only?
If the latter, you might want to think about having a new policy of leasing to one person only, regardless of the size of the apartment. In that way, if they choose to have a roommate move in, it is their business, not yours (unless occupancy limits are exceeded). If you had that as a policy, your cooperation would be extremely remote…and I think that any culpability you would have would be virtually nonexistent (about the same culpability as a taxi driver who takes a woman to a medical office building…
not knowing that the tenant of the building she is visiting is a GYN who is going to give her an RU-486 pill).