i'm a graduating medical student in california (at UCSF). UC medical schools are extremely expensive and, to me, are public in functionality but private in cost (one year at UCSF, including living expenses, is about 75k). i'd recommend looking into the UCLA david geffen scholars program - it provides full-tuition scholarships for about 30 incoming UCLA medical students per year. another thing to consider, given your background re: immigration and your previously undocumented status, is the PRIME program at UC medical schools, which, at least at UCSF, gives students a one-time 20k grant in their final year. PRIME does extend medical school by a year, however, which is important to consider, because that reduces your attending physician-level earnings by one year. there are other schools that have great financial aid packages -- uchicago, michigan, penn, and cleveland clinic come to mind.
i am preparing to start my residency and am fairly fortunate, because i only have 150k in debt and am married to a high-earner with no educational debt. i am also pathologically frugal. many of my classmates have 200-300k, are not married or are dating another medical student with debt, and are trying to live in the Bay Area on a resident's salary. it's hard.
that being said, i spent much of my late teens and early 20s trying to find ANYTHING i could do that wasn't medicine, because i knew of the financial and lifestyle sacrifies required of the profession. clearly i never found anything i loved as much. nothing excites me or keeps my ADHD brain as entertained as medicine. it's hard, the hours are long, the hierarchical nature of the profession seems antiquated at times, but i really, really love it. i have no interest in retiring early; i just like to save money, be debt-free, and have the flexibility in the future to do the kind of medicine i really care about.
one thing i wish i had done as an undergraduate is explore the other possibilities in the health professions, as people have mentioned. i, too, attended an elite college as an undergrad, and i found that the general refrain was "if you like science, you should be a doctor." nobody talks about being an NP, PA, CRNA, etc. while i do think medicine was the right choice for me, i agree with the sentiment above that you have no idea what medicine actually is when you're 21 years old, living on your parents' generosity, and relishing in an abundance of unstructured time.
one thing that i recommend is evaluating how hard you like to work. i am not happy unless i am working really hard and my brain is 100% occupied. my philosophy thus differs substantially from that popularized on this forum (more freedom from work, fewer hours spent at work, hobbies outside of the office, etc.), but i value and respect that perspective and do think it has really helped me reassess my own professional goals. furthermore, it has allowed me to be more critical of the often insane working hours of clinical medical students and residents. do not go into medicine expecting to work 9-5. do not go in expecting to be paid handsomely by hour. do not go into medicine because you want to be a hero. go into it because you love it, you love patients, and you can't see yourself doing anything else.
also - small point, but there are no more subsidized federal loans for graduate students. congress abolished them in 2012. so expect interest to begin accruing immediately on any stafford loans you take out as a medical student.