I used to write erotic fiction novels as a ghostwriter back on upwork and elance around 3-5 years ago.
I kept this up for about 2 years, and got to the point where I had a single renewing contract, basically creating a back catalog for a client, just writing novels every 5 weeks.
Given that pace, I ended up getting a bit of RSI, as well as a lot of practice working with basic plot structures, and expanding them into full length drafts for submission. Don't be a ghostwriter - it's a racket. Instead, just self-publish, by using the following instruction manual as a baseline for avoiding some common mistakes.
This instruction is for 
It is basically an instruction for how I would go about self-publishing on KDP right now, given what I know.
What you end up finding here is a series of best sellers charts that have been 'drilled down' into the genre top 100 lists:
What you want to do after you've found your top 100 lists, is you want to scan them for tropes, and come up with a list of 10 books off of those lists that you would LOVE to read / write / stimulate your imagination, etc.
Then you want to deconstruct those books -- their basic premises, and structures, and tropes.
Here's an example:
Here's what I imagine this book is like:
Male Main Character POV - Target audience men who are into anime / hentai / harem fantasies / catgirls / cyberpunk / fighting evil corporations / appreciate tongue in cheek humor -- and women who are readers that are sympathetic to this sort of thing, or perhaps could find a way to empathize with the women and find attraction to the male protagonist.
Multiple women characters, multiple love interests.
Sometimes these books develop characters for a book, and then another character for another book, making the main characters basically serial polyamorists, caught up in a larger struggle and repeatedly falling in love and hooking up with these women while going on these larger adventures.
You want to get a bit more deep, talk about how the catgirls are a subclass with the bunny girls within the evil corporate police dystopia, and have your main character be instrumental in a revolution.
Nyaaa!
Project ought to be a minimum of 40,000 words to 60,000 words.
Write a rough draft first, following a rough 3 act plot structure.
Outline for 3,000 words a day, and then make a challenge, where you post once on HIVE each day your 3000 word draft. Do not edit until you get to the 60k mark.
Integrate comments from the community with a thoughtful edit pass and then Meme up an illustrated catgirl for the cover that is attractive, but not overly explicit / salacious -- because amazon will fuck your account.
Your blurb is basically a leading high level summary / movie trailer.
Your marketing is Keyword driven, and amassing a readership driven.
HIVE people who follow your blog get a free ARC copy of your book in PDF format via email, and you instruct them to leave a review that includes the phrase,
"I received an ARC copy of this book, in exchange for an honest review."
For bonus points, buy each of these people copies on kindle, and then gift them to the HIVE people, so you drive up initial sales, and get your reviews in. [This is questionable, and not necessarily needed, but may be useful.]
Include a link in the back of your book for your readers to join you on HIVE, where their upvotes and comments can participate in the creation of your next book!
MOST IMPORTANTLY -
Do not spend a bunch of time in this promotional phase. Because your next book is most important, always - next book, next book, next book.
It's still 'catgirl harem adventure' even when the subject switches to bunnygirls.
Keywords.
Bonus points if it's a litRPG, where the main character gets caught in another world that has harems of catgirls waiting to have sex and save the world with him, and he comes to the understanding that these catgirls are more than just projections of sexualized desire, but develops empathy for them, and uses this as a basis for a deeper romance, with each member of his catgirl harem.
.:.
BUT I DON'T WANT TO DO CATGIRLS.
You're in luck.
Here's the same thing except we swap out a catgirl harem for a barbarian alien race who all want to savagely fuck and marry and mate and hail as their queen, a bookish scientist female protagonist who got caught up in just the right circumstances.
etc.
Here's a deconstructed Romance Dystopian Version of the Hunger Games with aged up characters - Probably with lots of romantic tension and maybe even a good sex scene, turned into a 7+ book series.
.:.
You get the point.
TOOLS:
Non Negotiable - https://www.literatureandlatte.com/scrivener/overview
COVERS!
Get 10 covers of books that you are trying to sell like -- and then put your cover next to those 10 covers.
Can you tell them apart? If not, then publish. If so, then pay someone to make you a better cover.
.:.
Royalties are delivered out each after a 90 day waiting period, and then stack consecutively each month as you grow your back catalog.
In theory, your HIVE earnings ought to grow as well, as you bring on a more dedicated following to use the platform as a home base for your rough draft / manuscript development.
There will be a natural self-selection limitation [I'd guess], as most people will not be familiar or willing to onboard, and will prefer to just wait until the next Kindle book ships. [I might be wrong].
Try to ship one 40k to 60k word novel every 5-6 weeks, and do your best to serve the existing groups of people who already want to read the type of book that you want to write.
HINT:
The Alien Barbarian readership is not the same as the Catgirl litRPG Harem readership.
Best not to cross sections. Just stick to one, and write them a bunch of books for a year, and then reflect on your life choices afterward.
That's it. Good luck.
Also:
Stress that your HIVE work is DRAFT ONLY and different than the final which you ship to KINDLE.
This is because you want to be a part of Kindle Unlimited, and they have an exclusivity clause that says you can't publish your work anywhere else.
However, if you are simply writing chapter based drafts, which are edited into a final copy, which is not released anywhere except via KINDLE Unlimited, then you can probably have it both ways.
Cheers.
For more information please investigate: r/eroticauthors
It's a goldmine for self-publishing, and they all know that longform romance novels are the way to go for getting actual income.
