Entrepreneur (Patreon)

However in five of them it's illegal to be a customer. This was put in place partly because it's a bit of a grey area whether the prostitute is always willing or possibly forced to do it, but a customer is always willingly using a prostitute.

In most European countries it's perfectly legal to be both a prostitute and a customer though, but illegal to own a brothel or be a pimp. If the prostitute has to hand any of their money over to anyone else besides the government in the form of taxes, that other person is in big trouble. Here prostitutes are considered self-employed entrepreneurs.