from Rabbi Yosef Yeshaya Braun
A shadchan, one who arranges a shidduch, match, should be paid for their work. There is a clear halachah in Shulchan Aruch that a shadchan should be paid a brokerage fee, as any other type of broker. The amount to be paid is determined by minhag hamokom, according to the going rate in that community.
If one asks a shadchan to arrange a shidduch, the shadchan acquires the halachic status of an employee and certainly has to be paid. This applies to anyone who makes a shidduch, not only a professional shadchan, but even a friend, a colleague, etc.
It is customary to pay the shadachan after the shidduch has been concluded. Even if, chas vesholom, the engagement is subsequently broken, the shadchan does not have to reimburse the parties; in case the parties have not paid the shadchan previously, they should pay now, as they have been the recipients of the shadchan’s services, despite the fact that the shidduch later fell apart.
If more than one person was involved in making a shidduch, the custom is to divide the shadchanus gelt, money, equally among them. For example, if three people were involved, the one who initiated the shidduch, the one who helped the couple during the meeting process, and the one who helped conclude the shidduch, each of them should receive a third. However, only someone who actually did work to bring the couple together should be paid, not someone who simply made a suggestion. Nonetheless, a person who came up with an idea for a shidduch that was concluded should receive something in appreciation.
i heard that $1000 from each side is the minimum asking price (and if you say you will pay more (give a $1000 tip) you will get much better service)