In general you want to have at least 100 max bets for around a 5% RoR. That usually means 800-1200 minimum bets. So if you play at the $5 tables you would want at least $4000 for a $40 max bet or $6000 for a $60 max bet, etc. If you want a lower RoR then you will need more money than that. It all depends on what your EV and SD are for the game you are playing.
-Sonny-