My 23 year old daughter is moving in with me for a year or two after which time I suspect she and her boyfriend will begin their lives together in earnest. She knows how I live and has repeatedly told me it is a non-issue for her.Therefore nothing is likely to change other than having her sporadic company over a meal we can align on or some movie we might both watch. She leads a very private life and can spend hours on her own much as I can.
It might feel odd at first as I have lived alone for quite some time. I know it's likely to also be interesting for her and myself to live under such changed conditions. After all, when we last permanently lived together under the same roof she was only 10 years old.