I was deeply moved by your concerns about my question. Srna, thank you for your advice, and I will also have to consider community college or satellite university.
After listing about your advices, I visited several universities' web sites. Since I will live in the San Francisco, I am taking two universites into my account ; University of San Francisco and San Francisco State University.
I am feeling like I need to take statistics and science classes such as chemistry, organic chemistry, unorganic chemistry, biology, etc.
In the former school, there is a pre-health special course that offers those classes need to the persons who are supposed to go into health-related graduate school - medical, phamarcy, veterinarian, and so on. However tuition is so high- more than $10,000 per year. And there was no accurate admission requirements on the site.
In the latter school, I am considering about transferring to the Chemistry department as a junior, at the same time, as a second degree seeker or not. Tuition is just around $ 2, 000, however, I am afraid of thoughts of the possibility of class' difficulty to me.
I hope I could hear of your wisdoms.