Two SNG Questions

[PokerProdigy]

I am just starting to play single table tournaments of the no-limit hold'em variet, and I have two questions on the topic.

1) How many buy-ins (bankroll) should one have to play these tournaments?

2) Are the $5+1 sng's profitable? The reason I ask is because that's 20% entry-fee of the buy-in and I was wondering if this would make it impossible to play for profit, or maybe a negligible profit. Just let me know.