• The side hustle has become a popular supplement to full-time work, often in the form of starting a business or freelancing.
• Successful side hustlers excel at their full-time job first to ensure that others don't question their extra work.
• Keep your hustle and full-time career in the same circles, keep a strict schedule on and off the clock, and focus on the quality rather than the quantity of your work.
• Also remember to practice good self-care techniques while working around the clock.
• Click here for more BI Prime stories.

Taking on a second job while already employed in a full-time position used to be called "moonlighting." Today, it has morphed into the near ubiquitous side hustle, a practice that has exploded in the gig economy - with a new twist. Instead of doubling up by working for two employers (one after hours), the side hustle now often refers to launching your own small business or startup and/or taking on freelance gigs.

A 2019 report from Bankrate.com showed that almost half of US workers now rely on a side hustle for extra cash, whether to pay their bills, boost their savings, or have discretionary funds at the ready.

Business Insider tapped three part-time freelancers with high-paying side gigs to find out what this modern-day moonlighting looks like in practice - and how to make these two seemingly conflicting roles fit together seamlessly.

Complimentary Tech Event

Transform talent with learning that works

Capability development is critical for businesses who want to push the envelope of innovation.Discover how business leaders are strategizing around building talent capabilities and empowering employee transformation.Know More

Excel at your full-time job first and foremost

Talya Miron-Shatz is a professor at the Ono Academic College and CEO of her startup Buddy&Soul, a platform for personal development, and earns a comfortable six-figure salary. She's also a freelance consultant on patient and prescriber behavior. She does consulting work through her own company and consults for other companies as a freelancer - and brings in $10,000 or more per side project.

She suggested that if you go above and beyond in your full-time position, it helps to create goodwill among colleagues about your freelance activities as well.

"Your boss might be wondering why she's paying you full time when you're otherwise engaged," she explained. "Don't get there. Be sure to give your organization all it deserves, and then some."

To this end, Miron-Shatz said that she works hard to be the "most productive faculty member at the school of business administration."

"I bring in grants," she said. "And since I study medical decision-making, which is a hot topic, especially now with COVID-19, I'm constantly interviewed, which goes through the college PR and everybody sees. This way, nobody flinches when I am also CEO of Buddy&Soul, or tells me it comes at the expense of my performance."

Create overlap between your role and freelance work

Miron-Shatz also suggested that you can simplify your life by creating synergy between your dual roles.

"Promoting two careers is hard enough, but if you do it in parallel, it's easier," she said, pointing out that if you're a carpenter who writes poetry, you can't exactly pander your rhymes to people who come in for custom shelving.

In her case, she avoids this disconnect by ensuring that everything she does - both as a professor and an independent contractor - revolves around medical decision-making.

"My day job is at the faculty of business administration, where I study medical decision-making and teach consumer behavior. I have over 50 academic publications, which create unique knowledge and give me expertise and credibility, which my consulting and my startup benefit from," she shared.

Practice strict time management outside your 9-to-5 - and be ready to hustle

In addition to working a full-time job as a lead UX designer for a Fortune 500 company, Becky Beach also runs two businesses - an ecommerce store and the blog Mom Beach LLC, a work-at-home resource for moms that gets more than 50,000 pageviews per month - in her spare time.

"The reason why I started side hustling was because I was wasting too much time watching TV after work and wanted to do something productive," said Beach, who has, since launching her business in the summer of 2017, made over $500,000 in sales through her online boutique and makes over $1,000 a month with her blog. As a result of her successful side hustles, she has paid off over $150,000 in debt.

While acknowledging that she makes a full-time income from her side-hustle businesses alone, she finds her day job as a UX designer "very satisfying," which is why she hasn't left her corporate job to become a full-time freelancer.

Doing double duty like this does take some planning, though. The UX designer and blogger starts the day by getting up at 4 a.m. to work on her freelance businesses. Then, she works on them again during her lunch break, and at 8 p.m. after her four-year-old son goes to sleep.

Beach practices "time blocking" to accomplish all of this, which involves dividing her day into discrete blocks of time dedicated to a specific goal or task. The theory is that this approach helps you avoid wasting time figuring out what to do and when, given a long to-do list and conflicting priorities, since you've already indicated on your schedule exactly what you plan to do with each hour of your day.

And it works for Beach. "I will use the Pomodoro time-blocking method to distribute my time into 25-minute blocks," she said. "For five minutes between my blocks, I will get up and stretch and walk around the house."

The 25-minute time block favored by the Pomodoro Technique is thought to be "long enough to get meaningful work done, but short enough not to exhaust a person," The ONE Thing blog states - a good benchmark for freelancers who have limited hours to get their client work done.

Focus on quality rather than quantity of clients

In addition to time management, figuring out an effective approach to client management is another piece of the puzzle for those who are both full-time workers and freelancers.

According to Peter Czepiga - who works in marketing full time as growth marketing senior analyst at Bespoke Post, a men's subscription and ecommerce brand, and also freelances as a part-time media buyer - a key part of client management requires limiting how many freelance clients you agree to take on.

Czepiga, who is currently freelancing for the culinary brand Momofuku, helping them leverage paid social ads to drive online reservations, said his biggest piece of advice to avoid overdoing it is to work with only one freelance client at a time. With this in mind, he tries to keep his freelance rates competitive; depending on the job, Czepiga charges either a percentage of media spend or bills hourly at roughly $120 an hour, working between eight to 10 hours a week. This nets him roughly an extra $1,000 a month on top of his full-time salary, or around $12,000 more a year.

"Freelancing is a saturated and competitive way to make a living," Czepiga said. "Since you are selling your time, in order to produce high-quality work that meets your client's expectations, it is far more productive to build one deep client relationship rather than produce low quality work and leave multiple clients dissatisfied."

Czepiga admitted that in the past, juggling several clients led to his own underperformance across the board, which resulted in actually losing multiple clients simultaneously.

"I thought multiple clients would be more cost effective, but I was stretching myself way too thin!" Czepiga said. "I have been far happier and found far more long-term success since sticking with my one-client-at-a-time approach."

He explained that the way he parsed his client list down to one was simply by being pickier about who he worked with. A good way to go about doing this is by raising your rates.

"The odds are that you are undervaluing your services in the first place, and clients who truly value your contributions more will be more willing to compensate you at a competitive rate," Czepiga said. "Clients who are looking for a cheap fix rather than a long-term partnership will likely drop off." In either case, Czepiga pointed out that it's a win-win situation because you can then reinvest that freed-up time back into your one quality client.

Czepiga also advised that it's important to make sure you understand the scope of work that your client expects from you so that you have a good idea of when you should start looking for new clients. In his case, he asks his clients to provide a rough timeline of how long they expect to need his freelance services.

"Once I have that peace of mind, I can stop worrying about business development/onboarding potential new business and focus on performing the highest quality service possible for my client," Czepiga said.

Practice self-care and don't overdo it

Taking intentional steps toward creating better balance - between not only their two roles but between their personal and professional life - becomes critical for people who work full-time as well as freelance. Otherwise, they risk burning the candle at both ends.

"To succeed in a career - and even more so, in two careers - you need to have some mental reserves," Miron-Shatz said.

But how can you make this happen in a world where there is always reason to stay by your desk? Miron-Shatz explained that it's about creating good habits and sticking with them. With this, she exercises daily through swimming, yoga, or walking.

"I never skip exercise more than twice a week. When I get to work out with my daughters, that's a bonus," she shared.

Another way that Miron-Shatz preserves mental reserves is by carving out Friday night as date night with her husband.

"I never work that evening, ever - which keeps me sane and gives me a mental relaxation horizon," she said.

Another self-care rule includes not pulling all-nighters - a lesson she learned the hard way.

"I did this once for a huge project, which was presented in the UN Special Assembly on non-communicable diseases," she said. "Sleep equals health plus sanity."