Two things to think about
:
An employment-based green card usually requires a job offer (unless you are an internationally achieved person...). Have you checked if you need to keep working in that profession for a certain amount of time to keep your green card once you decide to go back to school? Some green cards are issued conditionally for two years and then have to be renewed, which is only done if you still meet the initial criteria.
If you want to go to pharmacy school just to get a green card, why not get a cheaper degree that would qualify you for a green card as well? Teachers with a Master's degree qualify for employment-based immigration in the same way that pharmacists do. (
Employment Based Immigration second preference category, see "members of the professions") You could get a Bachelor's degree in a subject you would like to teach along with a teaching certification for secondary school, and then get a Master's degree in the subject you would like to teach (e.g. biology or chemistry). A good number of colleges offer scholarships to international students and if you are not limited to accelerated pharmacy programs, you have lots of options to choose from. Graduate programs in sciences often come with full funding through e.g. teaching assistantships, which are usually open to international students as well. If you chose that path, you could potentially save a lot of money and you would acquire some valuable people skills while teaching that can serve you well once you become a physician (or whatever you want to become after med school).
On the other hand, if finances are not that big of a deal, I see the advantages of going to pharmacy school first since it overlaps quite a bit with med school. But is pharmacy school that much cheaper than med school?