Women who trade sex don't always do it in exchange for cash. A woman who sleeps around for any reason falls in to this category. Those who do it for money are just a little more honest and frankly admirable than those who do it for whatever other reason.
The problem with that logic is it applies to wives as well; who demand a higher price for their services than the harlot who only asks for a meal or a fixed price upfront.
I know you're looking for scripture here but the word study pretty much lays it all out there. Also, the text doesn't really reference a monetary exchange.
I did as you suggested. Looking at how it is used and the lexicon, the word as used in scripture seems to cover everything from adulterers to temple prostitutes to ordinary prostitutes to women just sleeping around. Problem is, the law treats all of those very differently (from the death penalty to no punishment at all) and somewhat inconsistently when it comes to transgression. It strikes me as a rather overly broad term.
So then do the 90% of Christian fathers whose daughters do not marry as a virgin; are they running afoul of Leviticus 19:29 then?