If there is no marriage you have absolutely no rights under US immigration law. US immigration grants no rights to friends, associates, partners, common-law spouses, etc. You are going tohave to marry him to have any legal standing.
That said, if your partner gets a student visa (an F visa) to study for an MBA, you can be issued an F-2 visa (spouse of student). This gives you the right to live with him in the US for as long as his visa is valid. A student visa does not lead to citizenship.
If your partner obtains an MBA it may be possible for him to be petitioned for an H-1 visa (expert in field). This will extend his stayin the US and allow him to work for the company that petitioned him. After a few years in that status, the company could petition him for legal permanent residency (LPR status) in the US. As his wife, you would also gain LPR status if he is granted it. Five years of LPR status gives one the right to apply for US citizenship.
