Emigration to foreign country and bona fide residence

I am a U.S. resident, and my income is foreign earned. I work on a ship in Brasil. I am researching bona fide residence, and found that I am required to live in that country or the country in which I am working for 330 days. I am wondering if this is for each year, or just the first year of bona fide residence. Also, what do I need to prove that I am a bona fide resident without necesarily buying a house? Thank you very much for your time.