i agree with mud here..

playing SNG's solely is EXTREMELY difficult. your payoff and risk ratio per tournament is extremely small in those tournaments unless you're playing in the multi-table version.

if you want to play to provide an income in this game, i feel cash game is the way to go.. and if you want to play NL cash games you need to have QUITE a significant bankroll with the LAG players you'll come across.

also.. dont get in over your head.. no matter what you decide to play in, play at the level that your skill is the clear favorite against the opposition.

you want a pretty decently sized bankroll either way whichever you decide to do, especially online.