All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Your question included some matters and we will summarize our answer to them as follows:
Firstly, it is permissible for one to work as a broker between those who are looking for a job and those who are looking for employees. The broker may take his commission from both parties or from one of them only according to they agree on. However, the party from whom the commission is taken must be aware of it, and taking it without their knowledge is not permissible.
Thus, if you tell the job applicant that the salary is 60/hour and tell the employer that the salary of the employee to pay 90/hour, so that you take the 30, then this is not permissible. Nonetheless, you may ask for a commission to be taken from the job applicant or the employer or from both of them if you agreed with them on this matter.
Secondly, it is not permissible to help a consumer of intoxicants (alcohol or wine), in his work, by preparing the place for him, or the drink, tools, or anything else. Worse than all of this, is to do that with the intention of tricking the person to get what he wants after he gets drunk, all this is sin and darkness upon darkness.
Rather, a person has to take the legitimate means in order to get lawful earnings and Allah will facilitate that for him.
Thirdly, inducing employees during the period of the contract to leave their jobs and move to another one just in order to get a commission from them [for doing this] is not permissible, because it takes the same ruling of selling a product to a person [with a smaller price] after he has already bought it from another person, or offering a lower price to a product after another person has already offered a price to him [and there was an agreement between the two]. As stated by Shaykh Ibn Taymiyyah .
Allah knows best.