One of my close friend who is born on 9th feb 1976 at rishikesh india is moving to jupiter mahadasha, in 2013?

he has venus in 7th house. since he is of gemini lagna, is he under kendradhipati dosha. he has saturn in 2nd house, rahu in 5th house, sun and mercury in 8th house, ketu in 11th house and moon and mars in 12th house.his income has drastically dropped since september 2010. Is it a warning before the advent of jupiter mahadasha. can anybody help him in predicting whats stored for him?