I did it for a month and one of my best friends did it for a year or so. I gave it up because it has a very low return on the time commitment. You have to go to tryouts all the time during 8-5 on weekdays and most of the time it is a 100 people trying for 1-3 spots. I'm quite sure that it would be impossible to do if in medical school.
Also, I would be very suspicious of who asked you to do the modeling? Was it an agency, or a company? Mos tof the time an agency will ask you to come in and take some shots. They will then say that if you want to be really successful you need to get some professional shots done that could cost 300-400$, but they would be happy to do it for 200$.
If your actually looking to get into it in the bay area, my best friend models with a company up there and I could set you up with a tryout with them. Their good in that he actually gets work from it (JC Penney and Mervyns)