Actually, I came to US first for BA in biology since I gained award for biology when I was in high school in China. But last summer I did full time biology research in advanced biology lab and found that I don't really like it.
You probably were once interested in biology, so much that you got a full scholarship to study in the US. Once you work full time, you didn't like it as much as you thought.
I really want to get into the financial engieering master program, but my family can't afford the high cost of master education. Actually, I came to US for education with full scholarship from this college.
What make you think that you will like financial engineering more than biology once you study or get a job? How would you like spending ridiculous amount of time learning stochastic calculus or debugging
C++ code.
I hate to give any kind of advice without knowing all detail. Most full scholarship has some kind of string attached, what is yours ? Would it require you to go back to China or go on graduate school in biology ?
I don't think people would give money away for you to study biology so that you can study something totally different. Do read the fine prints of your scholarship.
Should I took the optional practical training year to earn some money to go for the master?
If you are able to find a job with OPT, why not find a job that finance related instead of a temp job. You probably won't make much money in 1 year to pay for those bloody tuition anyway.
When in America, do as the Americans do: put yourself into a massive amount of debt.
I'm of a different mindset: live within my means.
Since the poster is not American, I doubt she can get herself huge debt, even if she really wants to.
So the PhD route seems like the only choice. Do a research and see which program would provide you with full tuition scholarship. Then apply and hope to get in that program. Cost of living is not free and you still have to find a way to survive 5-7 years in a PhD program.
Sorry that it's tough on you but life is always tough specially for people without money. I have to say like it is. I don't want to say "Go ahead. Take that 60K loan and go to MFE". You may end up hating everything about FE. That would be a huge waste of your time, money and my advice.