More specifically:
What was the common background of prostitutes? Are there instances of prostitutes achieving a higher social standard through their job (than they would have otherwise)? Once someone became a prostitute, was that their profession for life?
Did individual lupae have a say in which acts they performed? Did they experience violence?
How much were prostitutes paid and what sort of cut did a madam take? Did pay vary significantly between registered/legal prostitutes and unregistered ones?
Did women have any access to male or female prostitutes? Was there stigma attached to men using a male vs. female prostitute?
Did this vary significantly by region (e.g. Rome vs. Thrace vs. Carthage vs. London) and time period (Kingdom vs. Republic vs. Empire)?
If this helps at all, I've read some of "Eroticism in Pompeii" by Antonio Varone, though most of it was about phallic representations, and read some raunchier poetry, though I don't know if parts of it went over my head.
We know oddly little about prostitution in Rome. We can tell that it was socially important and common--Pompeii's very prominent brothel, for example, and scattered incidental mentions in literature, such as Cato's injunction that young men should not be seen entering or exiting brothels (ie, be discrete). There is also a few mentions in the law codes, where prostitutes and pimps had a variety of social disadvantages, legal and civil. However, this does not describe the condition of prostitutes per se, merely their relation to the law. So any answer to your question (eg, prostitutes were enslaved, terrified and subject to constant violence) may very well be true but is necessarily based on conjecture.
We can say a bit more about high class sex workers, the equivalent of the Greek hetaira, Japanese geisha and Chinese yiji. These have a noticeable impact in the love poetry record, for example, the later books of Propertius' poetry make it pretty clear that his beloved "Cynthia" is one of these, and some have gone so far as to argue that virtually all of the "poetic loves" are directed towards them and not high class Roman women (I do not follow this argument). These women tended to be well educated, valued as much for their conversation as their beauty, and relatively independent. But even here we can't really talk about, say, pay scales.
Follow-up, were prostitutes mostly free or unfree?