^^if you're looking to profit, I know raw trout and salmon bought at lowest would yield a profit if you sold it at max... takes a few days to go through the G E, tho.
Depending on which fish you use to get 99 Cooking, it can be a loss of anywhere from 500K to 5M. 99 Cooking by bot would take around 5-6 days. (it bots in al-Kharid)