According to Alba Waba, there is a loophole in Islam that allows “Halal Hookers.” The loophole is Nikāḥ al-Mutʿah (Arabic: نكاح المتعة), which is a “temporary marriage,” where the duration of the marriage is pre-determined, and the dowry pre-set, and the husband can give the wife money, if he wants. (source)
Unfortunately, it is bullshit.