Pro's: both partners get to know more each other, if you end breaking up, hassle free either he packs up or you pack up, it depends who owns the house.
Con's: personally as a woman, i don't go for it. it will leave an impression to women, especially to the male society, as trash, if the partners don't end up together. But don't get me wrong i don't condemn this kind of relationships especially the women, because i believe that every woman who enters a relationship are true, honest and sincere and who wants anyway a failed relationship. it is the men who are not true, honest, sincere or maybe just one of their macho effect. :)