First of all, jus because you may have a 5 year B1/B2 visa does not mean that you are permitted to remain in the US for 5 years.  Your authorized period of stay in the US is guided by the I-94 you were issued at the time of entry to the US in that status.  The visa validity is for 5 years, meaning that throughout the validity period, you can make multiple entries to the US using that visa but each time your stay once you arrive in the US is determined by the I-94.  Secondly, in B1/B2 status you are absolutely NOT permitted to work, in any capacity!  If you become a college student, you need to be able to show the resources for paying for tuition and other related expenses without employment since you are not authorized to work.