Question About Green Card Application

Hi everyone. I need your help with a question about Green Card.

I will start my first job at a university after I graduate in August with my master degree. I will work with my OPT till next August.

My boss told me that they will start sponsoring my green card application at the end of my first H1B cycle so that I can get it in the second H1B cycle. Then how long can I get the green card? thank you.