What is the ruling on one who demands a share of money merely on the basis that he found a project for you?

If there is a contract between two parties for planning a project or striving to find one for a known fee, the project owner is obligated to pay the agreed-upon fee upon completion of the work. However, if there is no such contract, then it should be considered: if the person who performed the work is accustomed to receiving payment for their work, then the other party is obligated to pay the customary wage (ujrat al-mithl). But if they are not accustomed to that, then they are a volunteer in their work, and nothing is obligatory upon the other party.