The most common business model for Open Access publishing for long form outputs is via the Gold route which will mean that your work is immediately OA via the publisher's website. Typically, this comes with an associated fee known as a Book Processing Charge (BPC). This is a notoriously expensive way to achieve immediate OA for long form output types and the price of a BPC can range from £5,000 to £18,000 (see the OBE Dashboard). This will vary depending on the publisher and can also be affected by the permissiveness of the Creative Commons license. For example, if you decide to utilise CC-BY licensing for your book, this may be more expensive than CC-BY-NC-ND. CC-BY may be mandated for outputs if you are in receipt of funding from an external organisation. Please see the Funder OA requirements tab of this guide for further guidance on funder requirements for OA books.