After doing the job he demanded a large payment
Question

                I made an agreement with someone that he would do a job for me, then after that he demanded a large sum of money, but I gave him the amount that is usually given to the one who does this type of job. Is there any sin on me for that?.
Praise be to Allah.
    If this man is a professional and does this work for you and 
    others, then he is entitled to the usual payment, and he is not entitled to 
    any more than that. But if he is not doing this work on a regular basis, 
    then you should come to some agreement with him. This should be a lesson for 
    you in dealing with people, not to deal with anyone until you know what you 
    have agreed to.