You can earn 40$ per day all you need hard working with freelancer. If you talk about earn 40$ per day with bitcoin then its quite difficult to earn with bitcoins. Maybe its only possible with trading, Its to much risky but if you work with hard you'll surely earn this amount per day.  There are not much high paying jobs which gives 40$ per day. Most of the bitcoin jobs are low paying and we can manage our pocket expenses  with it.