Subsidy publishing is also referred to as vanity publishing. Under this model, you pay all the costs of publication (including marketing), but the publisher may pay you a ‘royalty’ – but it would be unusual if you actually managed to earn back the amount you invested. Subsidy publishers should be approached with caution, as they frequently feature at well-known blogs such as Writer Beware and Predators and Editors (or just Google 'Publish America Scam', and think about the possibly apocryphal story that Publish America accepted a compilation of shopping lists for publication, despite claiming that their Acquisitions Editors will "determine whether or not your work has what it takes to be a PublishAmerica book").
If you choose to publish through a subsidy publisher, they will determine the price of your book, and will arrange for your book to be listed on the major online stores (Amazon, Barnes & Noble, Smashwords), and in industry catalogues. But the responsibility for promotion will remain with the person who has the most vested in the success of the book – you, the author.
Those who choose to self-publish will be responsible for everything. You will either have to do it yourself, or pay (or bribe or beg) someone else to do it for you. This involves a lot of decisions, and you would be wise to get advice from someone who has been through the process before (and recently – things can change very quickly, particularly when it comes to e-books).
In terms of the product, you will be responsible for decisions around whether to publish a paperback, an e-book or both, and for arranging external editing and/or proofreading, then formatting, preparing cover graphics and the back cover blurb, and getting an ISBN number, either yourself or with external assistance. You will need to arrange the e-book conversion, printing and distribution.
You will then need to consider Place: where you are going to sell (online or through shops), Price, and then get on with the hard work of building your platform and promoting your book at the same time as trying to manage your personal life and write your next book. This can be a lot of work, but the rewards can be huge.
So, over the next few weeks, I will be looking at the basics of marketing books so that you understand just what it entails, and can begin to work towards your aim.