My fiancée and I are planning on moving out of our parent's house and into an apartment of our own after our wedding. During a conversation with a close mutual friend of ours, it was brought up that he will be going to school very near the city we had discussed moving to.
His program is going to take over several years to complete, and the commute from his current residence to his school is understandingly unappealing, as it would often involve an hour drive through a highway locally known to have bad traffic.
However, my fiancée and I are not quite sure about whether or not to accept his request to be our roommate. We enjoy hanging out with him, and do so quite frequently, but we do not know if he would be a good room mate as we both don't know what his habits are like around his home. We also value our private time together and do not know whether having him co-inhabiting will influence this.
Finances will not be an issue for the two of us, but I know he wouldn't be able to live independently once he goes to school. We're both not sure if we should give him a chance and see how things go, or just decline his request.
If we do decline, how do we decline whilst minimizing the effect on our relationship?
Note: This question is not asking if we should decline, but how to do so.