I did not say they are bad. I said they make selfish choices on such an extreme scale that such character lends itself very badly for marriage.
By being a hooker or an escort? LOL People become hookers/escorts for variety of reasons; sometimes out of necessity like Fantine in Les Mis? I know she's a fictional character but I am sure that reflected many of the women's situation especially at that time. And not all hookers/escorts are bad. Some of them became heroes saving their own country and many times sacrificing themselves. Your narrow-minded and discriminatory views about those women who were in that profession is not correct.
Trading is the wrong example to bring up. That's all I am saying.
So on the other hand if the husband/wife is fully aware of the other spouse's prostituting action and consents to it, then yes I would be fine with it because they wouldn't be bearing false witness and the other person (the john) would not be coveting thy neighbour's wife.