There is a saying that, One who aquires a slave for himself also aquires a master.
This also includes the knowledge that in Jubilee years that all slaves were set free. That would be every 50 years. If one aquired a slave the year prior to a Jubilee year, he would have to release that slave the next year. In addition, the master is responsible for the total well being of the slave and would be held accountable for it under the law.
The laws of Jewish slavery are not simple and have consequences for both slave and master.
No argument there. But I wince whenever people rip islam for "theocracy," "intolerance," "backwardness," etc., which are also found in the Torah.
The point is, all the Laws of the Torah are eternal, no matter how out of step with the contemporary world. Rabbi Yirmiyahu Bindman deals with these theoretical laws of slavery and polygyny (more than one wife) as they apply to non-Jews in his book, The Seven Colors of the Rainbow.