Agent taking payment for doing something on behalf of another
Question

                Is it permissible for an agent who does something on behalf of another to take payment for his work?
Praise be to Allah.
    It is permissible to appoint an agent with or without 
    payment. The evidence for appointing an agent without payment is that the 
    Prophet  (peace and blessings of Allaah be upon him) appointed Unays to 
    carry out the hadd punishment on a woman, and he appointed ‘Urwah al-Baariqi 
    to buy a sheep, without paying them for that. There are many similar 
    examples in the ahaadeeth apart from those that we have mentioned.  

    The evidence for appointing an agent with payment is the 
    aayah (interpretation of the meaning): 
“As-Sadaqaat 
    (here it means Zakaah) are only for the Fuqaraa’ (poor), and Al-Masaakeen 
    (the poor) and those employed to collect (the funds)…”

    [al-Tawbah 9:60]

    so those who are appointed to collect and distribute the zakaah are given a share of it as you can see.