The previoius answer is about what I would have said. Its not the book that makes the income its what you do with it and after it that matters. That is why social media is so very important, I have been doing just priming for 3 years, while writing pieces and blogs and giving my time away to help other authors for free to get my name out there. Everyone is different and it is true that they want to see what you can do before they want to do anything. I took and am still taking classes to understand the whole global process of this huge project. I wish you the very best and if you should need a book review I do them for free, professional and you get a copy and I will post for you if you are on Amazon or goodreads. Very best to you :)