Cheers flushy.
Yes i did't make it clear. (AS ALWAYS) I was talking about low limit cash games.
If you are playing fixed limit cash games a good rule is 300 times the big bet so for 5-10, 3000$ although i like to have more as i have an erratic style in limit cash.
If you are playing big bet games then it depends more on the style of the game, is it a wild game where the average pot is 100 big blinds, or is the average stack 10 bb's!
These are all factors to consider, but its a fair assumption that you dont really want to go below 20 buyins for any game.