Chapter 90 : Laws Concerning Doing Your Needs Where No Melachah is Involved Melachah Done Through a Non-Jew PDF download
You may say to a worker: "Do you think you can join me this evening?" though he thereby understands that you intend to hire him for work that evening, because only a direct proposal is forbidden. However, you may not say to him: "Be prepared this evening," because that is comparable to saying explicitly that you wish to hire him.
If you hire a worker to safeguard something for you, the worker is forbidden to receive wages specifically for Shabbos. But, if he was hired by the week or month, he may include his Shabbos wages with his weekday wages.