Is it permissible not to pay the 500 Riyals agreed upon with the friend after the employer breached the terms of the agreement?

It is permissible to act as an intermediary in job searching for a known fee. This falls under the category of a permissible جعالة (stipulated reward or commission) provided that the amount and duration are specified. However, if the amount is paid monthly without a specified duration, it is not permissible due to the uncertainty (gharar).

The intermediary is not entitled to the agreed-upon fee unless the work is completed fully as per the agreement. If the agreed-upon work is not completed, the intermediary is not entitled to the agreed-upon fee. However, if the person remains in the job, the intermediary must be paid a customary wage (ajr al-mithl) for her mediation, which is to be determined by experts. The agreed-upon amount is not binding since the agreed-upon work was not completed.