There are a lot of Americans who are wrong of the meaning of "Doujin" or "Doujin-shi". "Doujin" is not a meaning of the comics. "Doujin" is a meaning of the member and coterie. "Doujin-shi" is a coterie magazine.
There is often a foreigner who has misunderstood the meaning of "Doujinshi" as the book on fan art. Both doujinshi which draws an original character and doujinshi of fan art are called doujinshi. Japanese-language is difficult. Therefore, foreigners might not accurately understand the meaning of doujinshi. A lot of fan art doujin books are published now. Therefore, foreigners seem to have misunderstood the meaning of doujinshi because they saw these books.
It is a book published at its own expense. The content of the book is not limited as the comics (Novel, Poem, Autobiography, etc.).
These books do not circulate in a general bookstore. Non-commercial printed material.
Basically, these are amateur's publications (However, there is a case where a professional artist publishes the book by the hobby. ).
Book on hobby bought and sold by companions who have the same hobby.
You must confuse neither "Books sold in commerce" nor "Books printed by the hobby".

Often, I see the web pages to which this is written as dojin.
However, the meaning of dojin is "A native" or "Aborigines".
If coterie is accurately written in Japanese language, it is doujin.

Comic doujinshi is chiefly sold in the comic doujinshi convention.
The most famous comic doujinshi convention in Japan is "Comic Market".
This convention is held twice a year.
It is the largest comic doujinshi convention in the world. (400,000 people/two days)
Besides this, some medium scale comic doujinshi conventions are held in Tokyo.

In Japan, why can the individual easily make doujinshi? Some the reasons are thought.

*1. There are a lot of printers who undertake the book published at one's own expense in Japan.

*2. The print fee is cheap. The quality of the print is considerably high-quality. (The print fee is cheaper than the United States. Therefore, there is an American soldier who comes from U.S. bases in Japan to these printers. Those American soldiers might be otaku. They are printing doujinshi there.)

*3. The comic conventions (Comic Market, Comic Revolution, Sunshine Creation, etc.) are frequently held.

Therefore, everyone can make doujinshi.

Ordering to the doujinshi print shop in Japan if you hope for publication in independence might be good. However, a Japanese-language ability might be necessary for you.(^ ^;)

However, various problems began to occur. There are a lot of people of otaku who think little of the tax and the copyright. There are foolish people who cause arson and the commotion. I have a headache.