depends on your city/county about permitting and height restrictions (and setback/right of way from the road), but definitely get the property line demarcated first.
ive had cool neighbors that i didn't mind having a permeable border with and had complete weirdos who get drunk and stare without waving back, try to take and claim ownership of things, and let aggressive dogs run amok. or just invite a constant stream of new sus people over to be sus with. i don't have nice things, but ive had my place broken into by a neighbor's associate before and they seem to have gotten pretty frustrated that i didn't have nice things and took that out on the things i did have.
a nice privacy fence isn't going to stop you from being friends with a cool neighbor.
