There is a wide range and you might want to start by taking a look through the erotica section on the Amazon Kindle site. There is some stuff for free, but the page count on many of those are quite short (13-25 pages, sometimes more). The free books are basically to create a demand for either that book or the work by that author. It is quite common practice for authors to do an initial distribution of ebooks on Amazon for free to get their download count up (the more popular the book, the higher it appears on lists when searching).
Prices vary, but typically for a few dollars. If you sell something on Amazon for under $10, the author gets a 70% of the sale price, which is a game changer in many ways as typically the author's commission is much lower. Over $10 and you receive a 30% commission. Optimal pricing is still an area under exploration in ebooks. Pricing is all over the place as different companies try different approaches. It does in part depend on genre as I've seen teen ebooks selling for higher prices than the paperback version, but academic books selling for 25% of the paperback version.
If you price an ebook for $4 or $5 dollars (or lower), it is basically seen as a low-risk purchase at that level. ebooks are great as well, as people can read them without it being obvious to others what they are reading. I understand that women are a significant portion of the erotica market... though maybe 'True Tales of a Vancouver Courtesan' would reach a wider male audience (promote it on here, maybe). Look at the popularity of the 'Fifty Shades Trilogy'.
Cover image is important, even for ebooks, as that is a key aspect of drawing a potential audience in. And make sure it is carefully proofread, as typos and grammatical errors will quickly turn off your potential audience. Cost of editing varies. My wife edits student papers for about $30 an hour, but that price can be negotiated down for longer projects in the quieter periods.
The starting point is probably doing some research on Amazon to see what there is, what is getting the better rankings and what seems to be hot.
Also, a piece of writing software you might want to consider if you are seriously looking at this is Scrivener. Apparently it provides a much more natural approach to writing than the linear format that Word provides. I am about to test a trial version (they give you a 30-days of use trial for free) to see if it is as good as some of the reviews for it. Not too expensive either at $45 for the Mac version and lower for Windows (originally for Mac, and that version has more features).
Feel free to PM me for more thoughts or feedback.