When can a Catholic not marry but live together?

Answer 1

This is a question of discipline. It would depend on how liberal your parish priest is, but strictly speaking he must refuse to marry until you cease cohabitation for a time. This is because you and your partner have given public scandal by living together in the community in violation of Catholic moral standards. Even if you and your partner have not had intimate relations, the scandal is nonetheless present and public. If you cease cohabiting the priest will no doubt permit a marriage in due course, probably very soon as per your request. If the priest is liberal, or does not know your living situation prior to the wedding, and marries you without addressing this concern the sacrament is still validly administered, however, this will compound the scandal and it would be very hard not to be committing a sacrilege by marrying while in such a state. It is best to talk to your priest, make a good confession and return to the moral standards set forth by the Church that your wedding may be as joyous an occasion as possible before God, men and you and your loved one.

Answer 2

Only in a platonic or non-sexual relationship.

Unless you are of blood relation or the age difference between you is so great as to remove all suspicion of impropriety, or you are under extreme duress (you are being persecuted, you would have no alternative but to live on the street, etc.) Catholics or opposite gender are not permitted to live in the same residence unless married. The reason for this is because, even if the relationship is pure, scandal is still given to the public. Priests, for instance, are not to marry couples that live together before marriage, even if the couple has done nothing improper simply because they have given poor example and public scandal by this lifestyle (whether or not this is enforced is up to the priest, and regardless if it is, after a short period of residential separation between the two parties any priest will marry the couple in the end as is to be expected).

Answer 3

Yes, after both parties make a good confession.