If you really need the money that bad, you will be able to give it 8 hours per day. There are 24 hours in any given day and you can live off of 6 hours of sleep.
Day job is usually not limited to 8 hours. Commute to work itself takes ~3 hours of my day. I've 3 other small android apps I need to support in my personal time. 8 extra hours doesn't seem plausible.