You always need to be very cautious about having friends living with you as a married couple for an extended length of time. When your buddy visits and stays as a guest, there’s usually a lot of close interaction between you and your friend as you make the best use of your time together. But what you call “hanging out and having a beer” also doubles up with what evolutionary psychologists call “mate guarding behavior”. Or in plain English, you’re having fun with your friend, but you’re also cockblocking your friend getting to your wife.
But if you let your buddy actually start living with you, there’s no way to maintain the cockblock. You can’t just hang out and have a beer every single day when there’s real life and working late heading up your personal chore list. So at some point your buddy and your wife are going to be left together minus you. Now it’s unlikely that as your car pulls out of the driveway leaving them alone for the very first time, that they will lock eyes across the cornflakes and head back to your bedroom for five hours. But if you give it a couple of months just about anything can happen.