I'm doing a bookmark series for sell in my web page or to give as gift if someone makes a big order. Is it worth placing on the market? Or the printing process is very expensive?

I also have another dilemma, this drawings will be characters of a novel that I'm working, and I don't know if wait to publish the book or instead would be more if I began to sell this drawings as prints, bookmarks and other things.

Thanks for your support beforehand.