I hope you find reasonable place to live. It’s always a challenge.

I hear you about adult kids but as long as you aren’t moving into the same apartment complex or buying a house across the street from them (that would be intrusive) I don’t think they’d have issue with it. I’d not even worry about his girlfriend . She doesn’t own their town plus I am sure she is just fine with it. She might have no opinion because she doesn’t know you well. I am sure she’ll be just fine when you move and she gets to know you more