Wow, 20 hours? Personally I don't think I can realistically create much on the side with a full time job. I tend to be extremely tired at the end of the work day. So I think my only option is to quit my job again :-(
Maybe it is also my sleeping patterns just don't align with jobs. Today I simply had to sleep around 9pm (home from the job at 8). Slept till perhaps 11pm. Now I feel reasonably fit, but to be at the office in time, it is time to go to bed.
I experience this kind of pattern frequently.
In fact I sometimes wonder if the biggest mistake of my life was trying to adapt to other people's schedules (also girl-friends who want to go to bed "early" etc). Thereby I wasted most of my productive hours.
My typical work day at the office is painful because I tend to be tired...