Earlier quoted context omitted.
http://nirmukta.com/2011/10/13/misyar-temporary-marriage-in-... A quick Google tells me they probably practice temporary marriage as well but call it something else (and details differ). Anyone actually knowledgeable, please chime in.
The article you link pretty clearly identifies this form of "temporary marriage" as being the equivalent of a long-term mistress relationship rather than an encounter with a prostitute.
No, because legally the spouse then has all the rights of a marriage (alimony, etc.) Prostitutes do not get alimony.