If you write and illustrate a book that's good enough, you will find a publisher instead of trying to start a business in a shrinking/dying field. It's not going to be rejected out of hand because the protagonists are black: there's plenty of black children's books, YA novels, novels, etc.

Or you could e-publish it online without needing to start a business.

These hypotheticals seem to be set up to say things people just want to hear vs. actual analyses of the market. Where are the wholes in industry that small black-owned businesses could take advantage of? Don't just say "more small black businesses": they really ought to specify at least a generic type or industry