Reference: Fataawa wa Rasaa.il Shaykh ‘Abdur-Razzaaq ‘Afeefee – Page 471, Fatwa No.8
Question: The Shaykh was asked about buying and selling in graveyards?
Response: It is permissible, however, it is better and preferable to place (deal with) appropriate matters in [their respective] appropriate places. So graveyards are places which the Muslim visits and where his heart is moved with emotion, causing him to remember the Hereafter and be far removed from the affairs of this world.