It's not as easy as you'd think. Good hands get beat. It's possible to streak and have maybe a week or two in a row that you'd win day after day after day. There will surely be ups and downs. Hopefully more ups, and you can maybe average out to making 40-60 a day. I wouldn't know, but off hand, I would think it would be a little more than low stakes to make that amount in a day if you only played for an hour or two at most. And easy for some might be not so easy for most others. I'm not sure there's anyone here at CC who can make the claim they average this amount in a given year.
1. Winrate, namely BB/100 hands
2. Number of hands played
3. Average time it takes to get dealt 100 hands
So (assuming 25NL) if you're making 17BB/100, you're making $4.25 for every 100 hands. For simplicity you play 100 hands in an hour per table and multitable, playing two tables. You're looking at $8.5 an hour.
Lately I have been playing low stakes limit tables to win enough to fund my NL tournaments. Seems easy enough to make ~$10 in a few hours, but I don't have enough records yet to say anything definitive.