I agree that it is best to keep KMP girls in their comfort zone if "sex" is the purpose...having dated 3, they are not as likely to be sex partners for the majority of the actual time spent together. And the Boyfriend as "doormat" rule does come up all the time.
That being said if you treat them like a commodity (i.e. shit - and get them "to buy into the deal" prior to things getting too comfortable, they know where they stand,... and they tend to stick to their end of the deal.) Hot Girls in general are like pack animals (i.e. dogs.) If you give them an inch (be a nice guy) they will eat you alive...and not even stop to wave goodbye as the dust settles.
But, with a bit of learning and skill (and never any money being exchanged) they will fuck, BBBJ, RIM, Even got some Anal, and if you are crazy enough, Fuck without a Condom (but I urge you all to shy away from that.)
I can't say any of these relationships end well, but they kind of level off.
You will have to spend time and energy (and of course some out-of-pocket...but other than the first drink or a burger, never get into the habit of buying these babes anything.) Do it once and you are done.
But yes, they will go out with you, but then it isn't the same as the fantasy at the "working house". Still they are exceedingly hot.