Like everything in poker, the answer to your question is "it depends." I regularly play at a B&M casino near Chicago and play $5/$10 hold'em. On a decent day, it's not unheard of for my to leave with a $200/day profit after 10 - 12 hours of play. Of course, I'm usually playing with 3 or 4 of the same guys every week, and I have a recent handle on their styles, and 2 of them are complete fish who are retired and are playing mostly for fun.

The answer to your question depends on the following: (1) game selection; (2) quality of players; (3) quantity of pros and/or knowledgeable players who frequent the room; (4) house rake; (5) travel expenses; and many other factors.

Perhaps the most important thing to consider is that right now, poker is in the middle of a huge boom, with a large number of fish in a growing pond. As I said earlier, I regularly bring home $200/day playing $5/$10, but I do this because the players I play with are horrible and numerous. In 5 years, I would be surprised if I was able to maintain this win rate as newer players grow tired of losing or go broke. Having said this, I know of no players at my local casino who make a living playing $5/$10, but personally know of 2 who make a decent living (i.e lower-middle class) playing $10/$20 limit. However, they acknowledge that they are usually playing upward to 12 hours per day, 6 days a week. Most are hoping to learn and acquire the necessary bankroll to play in bigger games ($15/$30 or higher) within the next year or so, as they fear that the poker bubble, like the .com stock bubble, will one day burst, forcing them to search for bigger games in order to earn their living.

Of course, all that I have said applies only to live B&M games. It may be possible to earn a sufficient living at low limit games online b/c you can play multiple tables at once and more hands per hour, the more you can make at lower limits.