In my experience, Id guesstimate 10% of the women in this profession are as you say, grounded, well balanced, and desperation plays no part.
One misconception I had, and I learned quickly,is that being a longtime monger, Ive always believed the more desperate a woman, the easier it would be to chop down walls and prices.(after all, we all want the best sex available for the cheapest price)
Not so, and Ive learned after being dumped by quite a few.
In my experience, (so noone jumps down my throat and claims Im wrong), this is only my experience, I find these truly desperate types, that decide prostitution is the only solution, have usually been fucked over by so many men, used and abused, that even though they can handle selling themselves, they arent one bit happy or glad to oblige anyone beyond what they think they have to do. Ill leave it at that.
Ive found the college type, like the one I described here, usually happy, willing to push her limits as long as it didnt hurt her, and shed profit from it.