Question about the WUSTL Department Transfer!

Hi I’m planning on applying to wustl(aka WashU) as early decision.

I’m planning on applying for the School of Arts & Sciences (for psychology) because although I want to major Marketing, I thought the arts&sciences division would be less competitive. Would it be easier to transfer to the Olin school of business after I get in? (if not, at least double major)

Also, btw, I’m an international student applying for financial aid. If I transfer, will my aid support me throughout?

Thanks a lot!