What's going to happen if he brings home other girls? If you bring home other guys and he becomes super jealous and vindictive? If you guys start messing around but he doesn't want a relationship so then he brings home other girls a few days later and you feel humiliated? Basically this situation would have to go so perfectly smooth in that you both 100% want the exact same thing that it's unlikely things would turn out that way.

I personally would never move in with someone before I knew them for a few weeks let alone before we defined our relationship.