Taking payment to recite kaddish

Hi,

One who is hired to recite kaddish for someone who passes away may accept multiple such "jobs". Each kaddish recitation should be assigned to a particular person for whom kaddish is recited, and at least one kaddish per day should be recited for each of them. Ideally, one should record which kaddish is recited for which person.
 
Note that the person reciting kaddish must notify his employer that he is only reciting one kaddish per day for that particular person, since the employer might have assumed differently. Otherwise, this could be theft.

(Rav Moshe Feinstein, Igrot Moshe Yoreh Deah 1:254)

Have a good day,
Mordechai