Being an entrepreneur has its rewards, but there will always be ups and downs. To mitigate the downs, create an additional stream of revenue that can supplement your business while you grow. This helps balance out some of the costs associated with running a company, while ensuring that you have a diversified source of income.

An estimated 37 percent of Americans work a side hustle as a way to make this extra money, according to a 2018 Bankrate survey, and the median rate an average person earns in a month from the side hustle alone is $686. Get extra cash-flow to grow your business, and keep your bank account full, using one of these 4 income stream options.

1. Sell Digital Products

An online store allows you to sell digital products, along with your services, all in one place. For example, you may come from a marketing background or be a finance whiz. With the an online store, you can sell your knowledge in the form of workbooks, ebooks, digital downloads and more. Not to mention, “an online store can be a powerful tool for centralizing your freelance business into a single website,” suggests Selz, because it allows you to consolidate your elevator pitch, and knowledge, in a way that is accessible and definitive. Plus, visitors will see what you offer for services, and may be more likely to become clients.

Before creating anything — which might not take money — narrow down your audience. “Identifying and defining the right audience helps narrow down the tasks you need to do to efficiently promote your products or services,” explains the guide, Digital Marketing for Ecommerce Startups. Do this the same way you did when identifying your ideal client: “[Create] an avatar of your perfect customer. Make sure to establish the age, gender, location, source of income, and personal goals to make it as realistic as possible,” says the same guide. With this information, you can create products that actually sell — not just take away from the little time you already have.

2. Create an Online Course

Resources like Udemy or SkillsShare have made it easy and convenient to create your own online course and sell to the masses. With your videos or slides and audio set, all you have to do is upload it, add your description, and wait for people to find you. The eLearning arena as a whole is forecasted to reach $240 billion in revenue by 2021, projects Global Industry Analysts, so this is one side hustle worth your time. Note that a portion of the enrollment charge will be retained by the host platform, but the residual amount is yours to keep.

If you’re struggling for topics, note that that you don’t need to be the ultimate authority in order to provide adequate, in-depth instruction—you just need to be able to teach it accurately and effectively. Focus on any subject in your wheelhouse, from how to speak fluent German or cook a vegan meal, to how to play the banjo or code in HTML. If you want to reach potential clients and customers, however, focus on a topic that’s related to your business, allowing you to show your expertise in that field and drive initial interest in what you have to offer.

3. Start Taking Freelance Gigs

The freelance world has taken industries across the board by storm. They make it easy to get help at a lower cost—no need for expensive benefits and salary—all the while, people like you are able to take on temporary work and bring in extra income. As a business owner, you can use your savvy to provide high-level business insights or even marketing strategy.

You can also take advantage of skills you may have learned before you started your business. Perhaps you were a developer or product engineer. These are skills you can easily translate to work found on sites like UpWork. Before jumping in, do some research to see if certain certifications might make you more attractive for potential gigs. Don’t forget that you can also tap into your current network for work like this. Reach out to old bosses and people you’ve met as a business owner. Knowing someone is always a good way to get work.

4. Record an Audiobook or Write an Ebook

Another way to share your expertise is through audiobooks or ebooks. If recording an audiobook is your speed, the Audible ACX marketplace enables you to create and distribute your content on retailers such as Audible, iTunes and Amazon. If you choose the ebook route, Kindle Direct Publishing circulates your book to Kindle stores around the world in 24 to 48 hours; plus publishing has gotten easier than ever as these platforms has evolved.

What’s more, this is a great income opportunity. Data from the Association of American Publishers, ebooks and audiobooks grossed $358.70 and $137 million in net profits as of 2018, respectively. Due to both the speed and convenience, an increased number of readers have opted to consume books in digital formats, which makes this stream of income a particularly strategic channel make money and build your brand as a business owner. The more niche the material is, the more competitive your audiobook or ebook will be, so make sure the content you produce fills a viable need within the business sphere.

Make Extra Money to Build Your Business

Running a small business is hard and an extra source of cash-flow can help relieve some of that stress. Find the idea that’s best suited for your skills and expertise and see where it takes you and your business.