I mean, one nice thing about a smart, money loving servant is that they are predictable. Chances are good that as long as you can ensure long term employment that is above most others they will probably stay loyal. Smart being they key point IMO. A smart servant will go for the long term investment rather than a quick flip. Plus with Yona not only is she getting paid more, she still gets to talk shit to her employer. Probably won't find that combo anywhere else.