Prostitution benefit include going away after sex
Benefit of prostitution is not just sex, it is partly paying her to go away after sex.
So if you even manage to secure her for 30000 Euro. I do not think she would be going away easily when you decide to cut her off the contract after one year or two. In State. She might team up with lawyer to even sue you for more money. Of course lawyer will get their legal fee payment with some % and most likely also including some sex or blowjob LOL).
I guess you can have fun with FKK girls outside club for fun for sometime. But long term deal like this may lead to trouble as it will be hard to get rid of her when you no longer require her sexual service or companionship.
In the end, Women especially those in FKK are all about money honey LOL