Welcome, Maristella! I think the majority of cases that I've seen or in which I have been involved depended entirely upon the neighbors in question. There seems to be a large class of people for whom the neighbor's playing and practicing causes no particular issues. Of course, on the other hand, there are occasionally the neighbors from hell who will not be satisfied until either the piano or its owner are gone. There is almost nothing that can be done to placate these people, and in extreme situations, I would recommend that the pianist seek guidance from the landlord or condo association.
Some buildings/associations may have specific rules that apply to the playing of musical instruments (I once had a lease that expressly forbade vocal instruction!). In certain cases I have heard of landlords and or associations requiring that playing/practicing be restricted to certain hours of the day. And then, there is the worst of all possible scenarios, in which the landlord is dead set against piano playing. I would always suggest a pianist to consult with the landlord or condo association before signing anything to make sure that the building is at least partially friendly towards one's piano playing and practicing. And for those people who currently reside in a building but do not yet have a piano, my advice is to ask one's neighbors, landlord and/or association if having an acoustic piano will cause any ill will or other problems BEFORE buying a piano.
You may want to move first!
Kindest regards,