A 30-year-old physician assistant who spent 7 years in school missed her 'prime investing years,' and she's not the only one

• Due to the power of compound interest, your 20s are your prime investing years.
• Kristin Burton, a physician assistant, missed out on her prime investing years, and she's not alone.
• If you haven't started investing yet, it's not too late.

Kristin Burton missed her prime investing years.

She graduated with $161,000 in student-loan debt after seven years of school, and for 16 months, Burton and her husband lived on his $40,000 annual salary in order to use hers exclusively for debt repayment. In addition to her regular hours as a physician assistant, she picked up extra shifts at her office and at four or five others.

She was free of student-loan debt by the time the pandemic started, but she continued to take extra shifts to pay off her mortgage. "I think at one point, I worked 15 12-hour night shifts in a row," Burton told Insider. "I was exhausted, but we needed people."

Even though she paid off her student loans and her mortgage completely, she regrets not investing in the stock-market earlier. With undergrad and grad school combined, she spent most of her 20s in school or trying to figure out what to do with her student loans in the first place.

"I missed a lot of the time that other people are usually investing," Burton said. "Even with just smaller amounts of money, there could have been huge progress."

Compound interest means investing sooner is better

"The power of compound interest is why your 20s are prime investing years," said Hannah Whatley, a financial planner at Rather & Kittrell.

Compound interest is also known as "interest earned on interest." For example, if you have $1,000 in an account that earns 10% interest each year, you'll have $1,100 at the end of the year. If you keep it in the same account for another year, you'll earn 10% interest on the new balance of $1,100, which means you'll have $1,210 at the end of the year.

From there, your investment can grow exponentially over time. But compounding interest can work against you in the context of student loans or credit-card debt.

Burton, who coaches other healthcare workers on navigating their personal finances at Strive Coaching, has found she isn't alone. Since launching her business, over 350 healthcare professionals have enrolled in her courses, and another 800 have purchased her financial wellness e-books.

"Almost all of us have six-figure student-loan debt," Burton said of her clients in the healthcare field. "Many of us have debt-to-income ratios of 3-to-1, or 4-to-1, and it's emotionally crushing to have that experience and not have any idea what to do about it. On top of that, we're in training for a long time, and we missed our early investing years."

It's better to start investing late than never

Just because someone isn't able to invest in their 20s doesn't mean they shouldn't invest. Starting in your 30s or 40s, or even in your 50s, can be better than never starting at all. Remember that for most people, investing is a long-term strategy to build wealth for the future, like retirement, and 10 or 15 years is certainly still a long-term target.

For anyone just starting to think about investing, Whatley recommended starting with an emergency savings fund first. An emergency savings fund is three to six months' worth of living expenses stored somewhere easily accessible, like a high-yield savings account, in case of emergencies or job loss.

Once the emergency fund is set up, you'll be in a strong financial position to start investing. Regardless of how you invest — perhaps index funds, exchange-traded funds, or retirement accounts — Whatley recommended automating your investments to make it even simpler. Set it, forget it (mostly!), and let compound interest do the rest.

And remember: If you're feeling behind with your money, you aren't alone. "A lot of people in healthcare graduated, just like I did, with tons of student-loan debt, no idea how to invest, no idea about anything with money," Burton said. "Honestly, it's overwhelming."

• Read more from Women of Means:
• 4 tips for busy moms who want to start investing, from an expert investor and mom of 2
• Women are underrepresented in investing — here are 4 ways we can close the gap and work toward equality
• I'm a financial planner and a woman of color, and I can tell you firsthand that investing is the way to build generational wealth
• My dad helped me buy my first stocks at age 8, and I remember what he taught me about money to this day