No, I don't offer advances. Royalties are usually about 25% of retail for black-and-white texts. Full color texts are more expensive to print, so royalties differ on those.
Yes, I have a contract. I'd rather not sign a contract with an author until the first draft of the text is ready for examination, as I need to set up a quick basic layout to estimate page count, in order to calculate royalties.
Authors are not charged "set up" or other fees. If I like the book, I will publish it at no cost to the author, and royalties begin with the very first book sale.
I don't sign non-disclosure agreements.
I am able to offer (with most titles) a discount so that authors can sell direct and make more per book.
I work with the author step-by-step (with author receiving pdf proofs) through internal page layout and cover design.
Authors are responsible for book images and must have all necessary copyright permissions. (Fair Use is never a good option for obviously copyright images, so don't rely on that.)
Cover design approval is ultimately the responsibility of the publisher, but I will work with the author; authors may hire outside graphic artists, but art must be submitted to publisher within required specs.
The author's job is not finished once the book is published. While the publisher will set up the initial marketing and distribution process (availability through Amazon and other online booksellers, marketing through publisher's website, etc.), it is the author's responsibility to continue marketing the book. I can give you ideas on this, depending on subject. (In today's online market, a solid author platform for direct connection with readers is absolutely necessary to create sales.)
It's better to query me when you actually have the first draft finished. Be prepared to make changes. I'm a publisher, not a printer.