It's really all very relative. It depends on what you do, how your brain works, your level of stamina, sleep patterns, dedication..... etc...
There is no one universal answer.
As a designer, sometimes I put in 16 hour days of back breaking work. Sometimes only 15 minutes. Some days not at all. Average is about 6 hours of design work (because my eyes are fried after that), and a few hours of other admin stuff. If I'm feeling crazy, maybe a few hours of fucking around.
Am I rich? Far from it. But I'm not starving either.
I think it shouldn't be too hard to reach your goal of $1k per month. McDonalds can give you that. If you can't make $1k per month with say, 2-3 hours of work 2 days a week, or 4-5 hours of work every other day, then you're in the wrong biz and should polish up the old resume.
I can make $1k in my sleep.
