Musannaf Ibn Abi Shaybah

Hazrat Iyas bin Mu'awiyah used to decide the right of pre-emption for neighbors, until a letter from Hazrat Umar bin Abdul Aziz reached him. It was written in it that do not decide in favor of the neighbor. However, if both are partners with each other or if the house is such that both have access through the same door, then you may decide in favor of the neighbor.