In June 2022, 28-year-old Lindsay MacMillan's dreams came true when her debut novel, "The Heart of the Deal," was published. MacMillan has wanted to be an author since the first grade and worked at investment banking firm Goldman Sachs for years as she wrote manuscripts and pitched them to agents. She left the company in March, and her second book is set to be released in 2023.

As she worked toward her goal of becoming a full-time author, MacMillan learned writing is not always a sustainable career. Her own book deals, for example, were "under $20,000" each, she says, adding that, "I make about $1 a book" after those advances.

As she launches into her dream career, MacMillan is looking into ways to supplement the income she makes from her books. "I call it authorpreneurship," she says, "approaching being an author in an entrepreneurial way."

Here's how she's building multiple streams of income.

She's booking speaking events

In March 2022, MacMillan gave a TED talk entitled "Love is Not a Business Deal." In it, she draws parallels between people's approaches to love and business, encouraging them to treat love not like a "commodity" but a "connection," she says.

The talk was a launching pad to book various speaking engagements covering topics like how your corporate job can catapult your entrepreneurial pursuits and how to carve out your unique career path.  

"Right now, I haven't been charging speaking fees," she says, "but for my events I'm lining up in the fall, I'm charging speaking fees at universities and corporations and retreats."

She'll be charging about $500 for a two-hour speaking event, and started booking paid gigs at universities.

She's doing one-on-one coaching

MacMillan also plans to build out a one-on-one coaching business for people who want to get into writing.

There are plenty of courses online and in person about how to be a better writer, she says. But there's a lot of business acumen involved if you want "to be able to actually walk into a Barnes and Noble and hold [your] book in your hand," she says, including knowing where that book could hypothetically fit on a shelf and how to convince an agent that publishers will want it.

"That's really the void that I see myself as filling," she says.

As an investor, MacMillan regularly went through the pitch decks of entrepreneurs trying to get funding. "We can learn from how entrepreneurs reach out to raise capital," she says as an example. She herself has pitch decks to agents for her books. She'll be charging $100 per hour for her individual coaching.

She's giving herself six months 'to just dive in'

As MacMillan builds out the multiple prongs of her business as an author, she's downsized her life significantly. She's moved back in with her mom in Michigan, for example, and is keeping her expenses to less than $2,000 per month.

"I'm giving myself kind of six months to just dive in and say, let me just play, let me explore, let me fling a lot of things out there and let me mostly focus on having this really successful first product," she says.

Check out:

This 28-year-old was making 6 figures as a vice president at Goldman Sachs—here's why she quit to write novels

How to do a job that's not your passion, says ex-Goldman Sachs employee: 'I got comfortable with being a good-enough employee'

This 34-year-old mom's Etsy store brought in nearly $160,000 in 2021: How she built her side hustle while working full time

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