Hi and thanks for this question. 
I especially enjoyed your refreshing openness in asking about a slightly ‘taboo’ topic (why taboo?!), and appreciate your trust in this community to respond well and without judgement.
There are references to courtesans and sex workers in the EBTs. Such as Ambapali of Vesāli who was reputedly very beautiful and could command huge amounts of money for her services, money she utilised to donate a large estate for the Buddha and his Sangha to use for practice. She later became a nun and attained enlightenment. There are other stories too in the commentaries, such as Sirimā, who was also very beautiful and very generous too, and became a stream winner. Even in death she continued to be of service, the Buddha (apparently) inviting monks to see her decaying body to help with their lust!
The commonplace interactions of sex workers with many levels of society in the sutras and vinaya seems to indicate they weren’t the pariahs some people see them as today. It’s important to remember that sex workers are just people like all of us and there is tremendous variation in the experiences they have of their profession. We shouldn’t fall into that easy and lazy trap of moralising whilst ‘clutching at our pearls’ in exaggerated horrror, or engage in ‘othering’ of them that makes these people seem like a different species (they walk among us!) And we definitely shouldn’t over simplify and generalise their diversity. Perhaps as with many groups that experience being stereotyped, it’s good to actually listen to sex workers and how they talk about their lives and craft.
As for sexual misconduct, in the 3rd precept it is not defined very clearly at all:
Kamesu micchacara veramani sikkhapadam samadiyami ,
Literally: “I undertake the course of training in refraining from wrong-doing in respect of sensuality.”
It is a training precept, not a biblical style commandment, although it is often presented as such, with many people making the mistake of thinking that because nuns and monks are celibate, sex must be somehow bad for lay people. But it’s just another form of sensuality. An intense form, true, using all the senses, but then, I’ve also seen people get pretty worked up talking about food, music and cars! 

In MN 41 we get a different but more full definition that focuses on adultery, sex that is against the law and sex with people who are ‘protected’ by family:
“He is given over to misconduct in sexual desires: he has intercourse with such (women) as are protected by the mother, father, (mother and father), brother, sister, relatives, as have a husband, as entail a penalty, and also with those that are garlanded in token of betrothal.”
In our contemporary society with poly-amorous relations and open relationships, online dating apps and swingers parties, Buddhists certainly have many opportunities to ‘contemplate’ the nature of their desire, but it is only misconduct if you are breaking a ‘contract’ with someone (like between spouses, or with a partner you’ve agreed to be monogamous with) or any behaviour that ‘entails a penalty’, which today would entail nonconsensual behaviour such as inappropriate touching, rape, child sexual abuse, and any sexual harrament in other forms. So it comes down to what your contract with them is (and any other partner you have) and if it’s consensual. A note of caution though on condemning sex which ‘entails a penalty’, remembering that it was only recently that gay sex was criminalised in many countries and still remains so in many today. So perhaps, focusing instead on the consensual is actually quite important even if it is illegal? Maybe that’s why the precept is kept vague, because it’s partly about relative standards of misconduct in societies and that definition changes over time.
Many people think prostitutes must be breaking this precept all the time (as married people often avail themselves of sex services) and make it out to be both sexual misconduct and wrong livelihood. However the sex worker does need to know about their client’s married status, and does not have a ‘contract’ with the client’s spouse, that is the sole responsibility of the client, who is breaking the precept, unless they have permission! Don’t blame the sex worker for the client’s actions.
It’s easy to understand why people seek out intimacy in a world so full of loneliness. We are conditioned even as babies to want to be hugged and caressed, not to mention countless lives of sexual activity… but therein lies our problem! 