Originally Posted by dj11
Conventional wisdom suggests a 100 bb bankroll.
100bbs? You need 300 big BETS for limit (= 600 bbs), and more for NL, although it is usually expressed in terms of max buy-ins, not big blinds. In this case, to play professionally you would probably want at least 50 buy ins ($10,000). The OP didn't say he wanted to go pro, only to play regularly, so realistically $5k is probably sufficient.
$20k is 100 buy-ins, so it's only a slight exaggeration.