This greatly depends on your experience level, how much work you put in every day, the type of business you are in, you're personal situation, and quite a few other factors.
If you're at the top of your game (you know what you are doing - have experience of 5-10+ years), I would say if the income does not come in after 3-6 months, you're wasting time and effort.
Otherwise it could take years to get things right before you find out that the market for your idea is not there.
If you're at the top of your game (you know what you are doing - have experience of 5-10+ years), I would say if the income does not come in after 3-6 months, you're wasting time and effort.
Otherwise it could take years to get things right before you find out that the market for your idea is not there.