Well I'm going to be promoted and my friend, whom I live with is already a manager, can we live together?

That's completely up to the company that employs you and their contract terms.

As noted, this is totally up to company policy. If company policy is silent on the issue, then management may make a decision based on whether there is a conflict of interest or not. Also are you just roommates or romantically together. That might have a bearing.

Generally as long as there is no conflict of interest or you won't be reporting to one another, it may be overlooked.