How far can I sketch before I can draw a cartoon?

That depends on the degree of comics, such as Xiaobai comics, which can be drawn without sketching (maybe you can make money, see in detail).

Second-rate comics, it is enough to grasp the proportion, and there are traces of muscle structure (probably enough). First-class comics, like Japanese ones, are more professional. Learn plaster casts. Then super comics, American comics, are not only plaster statues, but also various light and shadow muscle effects and backgrounds, and they also need to be colored (except black and white, rarely)

Another thing to mention is that comics are not so good to draw, mainly unique plots, appetizing pits and just right burial pits. It's not that the paintings are exquisite, but awesome, such as the attacking giants and the draft! For example, 100 thousand cold jokes, but personally feel rather pitted. There are also personalities and plots that the public likes. For example, there are more people watching the beautiful weather. I have seen a cartoon before, in which a little girl drew it with a pencil and took it with a mobile phone, and its popularity is even higher than that of hand-drawn board drawing.

I hope it helps you.