Diversify your income.
It's something often read about in books on business. If you're selling a product, then think about branching out and offering a related product. Maybe the widget you're making has an accessory, or another type of widget in the same category as the first.
But what does this have to do with books and authors?
Every book an author writes and publishes is a product. Sure, it's still a book, but it's not the same book. One of the reasons authors are told to write in series is because it's easier to get a reader to buy another book in a world they're already invested in than it is to try and get them to purchase a story with characters they know nothing about. It's also why authors are advised to 'stay in their own lane', i.e. don't genre hop.
While this isn't exactly the same as say a set of kitchen knives, there are a lot of similarities. Say the company making kitchen knives suddenly decides to make rugs. They're both household items, but one has little to nothing to do with the other. The company would essentially be starting their marketing from scratch. While they might be able to easily convince their current customers they need a knife sharpener to go with their knives, a rug might be a much harder sell.
The same is true when it comes to books. Not every reader of paranormal romance is going to love westerns. Not every reader who picks up a hot and steamy BDSM romance is going to run to pick up the newest sweet, no sex on the page, small town romance.
So how do you diversify your author income and still stay in your lane?
First, write in one genre. Two, if they are very closely related and have a lot of readers in common. A bigger backlist is like the knife company coming out with an exciting new knife for their customers to buy.
The great thing about this is that the more you write in one genre, the more trust you build with your readers. That means, if you do decide to pivot to a new genre down the road, as long as it's not a huge leap, more of your readers are likely to follow...even if it's not a genre they normally read.
As an author, there are a lot of other more creative ways to diversify your income. Merch is a big one. Once an author begins to gain an audience, offering merch to your readers can not only bring in more revenue, but can also aid in your marketing. Maybe your book has a catchy saying and you put it on a shirt or a mug. Anytime a picture is posted with that mug, or that T-shirt is worn, that's free advertising!
Another way to diversity your income as an author is to use something like Patreon. Back in the day *cough* artists used to have Patrons. These were people who contributed to artist financially in order to give them the time or money to pursue their creativity in whatever form.
Back then, these patrons were typically wealthy benefactors. Today, with the blessings of the internet, one doesn't have to be a billionaire to support their favorite artists.
Patreon works as a give and take between the creative and the patron. When I set up my Patreon, I did it with a goal of providing those who wanted early access the ability to get it. My readers can, if they choose, sign up to support me and in return they will get to read my stories as I write them, one chapter at a time.
If you'd like to check out my Patreon, see how I have it set up, How my tiers (benefits) are divided, or if you'd like to sign up to be one of my Patrons, click HERE.